Hidden Wire

The miniature microphone, as worn by an undercover officer or an informant, is the single most unreliable piece of technology of all time. They are prone to shorting out, smoking and sparking, bad reception and easy detection - but strangely, they are immune to clothing noise, although this is the primary handicap of their real-world counterparts.

The bad guys will always discover the microphone itself, never the much bulkier transmitter to which it is connected (usually about half the size of a box of cigarettes). Invariably, it is secured to the body using large swathes of white bandage, rather than the small piece of transparent tape used by film professionals. On the other hand, budgetary limitations often result in real police forces using surprisingly antiquated technology.

As a variant, a parabolic dish device operated by a technician at a distance is used to listen in on criminal conversations.

See also Engineered Public Confession, Incredibly Obvious Bug.

Anime & Manga

 * Angel Cop: Taki has a tape recorder inside a false cigarette box. He also bugs the villain via a microphone hidden inside a cigarette that he had left in the ash tray.

Film

 * Parodied in the Starsky and Hutch movie, when Huggy Bear goes undercover wearing a wire, consisting of a full size microphone and a huge antenna under his shirt.
 * The detectives in Se7en shave their chests so they can tape wires to their skin, prompting one of them to wonder if a shaved-off nipple would get treated as a work-related injury.
 * The film We Own The Night strained credulity with a bug and transmitter small enough to fit inside a functional cigarette lighter...in the early 1980s. Apparently, the NYPD is keeping all the good stuff for themselves.
 * In Oliver Stone's Wall Street, used a hidden wire.
 * The Conversation plays this completely straight and to its fullest. The plot centers around a discussion two people have as they walk through a park—without realizing they're being recorded by hidden and long-range parabolic microphones.
 * A variation occurred in the movie Singin in The Rain that lampshaded the worst parts of hidden microphones. While making their first 'talking movie', their lead actress had trouble being heard. First, the microphone was hidden in a plant, and she couldn't be heard because she "couldn't make love to a bush!" Then, it was placed in a poof of her sleeve on her left shoulder. Of course, when she turned her head to say "No, I cannot love you", she faded out and back in. Then, they put the microphone in a giant brooch on her chest and got a nice background of her heartbeat.
 * True Romance (1993). The battery pack for the wire worn by Elliot drops down into his underpants, and he keeps trying to push it back up again. Fortunately no-one notices.
 * In Carlitos Way, Lalin (Viggo Mortensen) wears a hidden wire under his shirt while speaking to Carlito (Al Pacino) at a nightclub Carlito manages. Carlito correctly guesses that Lalin is wearing the wire after just a few seconds when Lalin tries to lure him back into a life of crime.
 * Played with in Infernal Affairs. When Triad boss Sam's drug deal is compromised by an undercover cop, he smashes a henchman's plaster cast on a table, but finds no wire. The henchman is an undercover cop and he did bug the meeting ... by placing the wire outside the window and tapping out Morse code.
 * Parodied in Police Academy 2 where Mahoney infiltrates Zed's gang with a large microphone taped to his chest that periodically receives radio signals from local sports stations. Needless to say, this gets Mahoney found out.
 * In Con Air, the DEA Agent's wire is the size of a PC's hard drive. When he discovered and killed, Poe stashes it on the now Bound and Gagged guard so that he can be discovered.
 * In Tango and Cash, the title characters find a dead body which is obviously wired. However, when they are put on trial for murdering the man, the recording is not used in the trial - the tape had been swapped with a second tape, which had been assembled from various sound bites of things the characters had said on other occasions, pieced together to make what appeared to be an incriminating conversation.
 * The brain recorder from Strange Days can be related to a wire, being hidden under a wig.
 * Donnie Brasco: Donnie refuses to remove his cowboy boots on entering a Japanese restaurant. When the owner objects his Mafia colleagues savagely beat him. It turns out that Donnie had a tape recorder inside his boot, which he later plays, listening to the sound of the innocent man being beaten.

Literature

 * In the novel Hannibal Clarice Starling mentions during her shooting inquest that a man from another agency is wearing a wire. A FBI man threatens to punch him out if he tries that again.
 * In the Florida Roadkill novel Cadillac Beach, Serge is talking to an old family friend while he is at a meeting of Cuban-Americans plotting the overthrow of Castro. At one point Serge rips open the shirt of one man in the group, revealing that he is wired, and announces that the man is a spy. Of course, the group is so thoroughly infiltrated by Cuban intelligence that the only person in the group who isn't a Cuban spy is Serge's old family friend and they all know it, but they feel morally obliged to beat up the exposed spy anyway.

Live Action TV

 * Parodied in Three's Company when Jack wears one to gather evidence of a corrupt food inspector who threatens to close down Jack's Bistro unless he receives a bribe.
 * In an episode of Law and Order: Criminal Intent, Goren and Eames convince a woman to wear a listening device to help convict her lover of murder. When the device is discovered, the woman tries to pass it off as a tube of lipstick, however the suspect still attacks and (at the time) it appeared they both died. However the team does wonder if the woman had previously warned the suspect ahead of time and perhaps what they had heard was staged, giving the suspect a chance to escape.
 * In one episode of CSI, Warrick wore a wire to catch a judge who was trying to blackmail him into tampering with evidence.
 * An episode of CSI: NY had Danny's brother Louie beaten nearly to death. Investigation revealed that he had been wearing a wire while talking to the leader of his gang, getting the confession that cleared Danny of murder.
 * In one episode of Monk, Monk has to wear a wire in his tie, but he ruins the transmission by trying to clean a stain off the tie.
 * In another episode, Monk goes undercover as a reputed crime boss and speaks directly into his sleeve while describing every single detail in the boss' hotel room.
 * Parodied in a Mr. Show sketch, in which a rat leads a man to a hotel room for a drug deal, with a vast array of incredibly obvious bugs; the rat tells the perp to talk into a palm tree and takes his picture with a camera poorly hidden in an enormous sombrero. The perp is suspicious, but his fears are assuaged by a game of 'thumb-print tic-tac-toe.' (Despite the evidence, the perp is acquitted on an episode of America's Dumbest Juries.)
 * A policeman told Americas Dumbest Criminals of a drug bust where he was wearing two devices. The dealer insisted on searching him, found one of them and accused him of being a cop. He said it was a pacemaker. The dealer believed this, then found the other wire. The cop convinced him it was an insulin pump. The dealer said "Man, you shouldn't be doing drugs, you're ill!" Then sold him the drugs, and was arrested.
 * Ashes to Ashes subverts this, with.
 * On The Wire, two detectives buy an incredibly expensive wire, intending to use it and then return it. They plant it on a drug corner inside a tennis ball..
 * One of the episodes on Family Matters had Steve Urkel wear a wire when trying to infiltrate a gang or criminal enterprise of some kind. The criminals realized fairly quickly that Urkel was no gangster, first tearing off his (clip-on) earring and then opening his shirt to reveal the wire.
 * In another episode, Carl is assigned to an undercover operation with an attractive female partner. When the criminals reveal the diamonds, more than once he repeats the code phrase "They look real to me" right into the location of the microphone—which happens to be on her breasts.
 * Particularly nasty example in '80s cop show Houston Knights; the person wearing the wire was a civilian volunteer helping the police (partly because he had a romantic interest in one of the cops). Partway through the discussion, the wire malfunctioned and started sparking, and he was immediately shot and killed.
 * One Australian mini-series involved a married couple who'd been convinced by the Australian Federal Police to help them gather evidence against a drug smuggling gang in Thailand. While talking to the smugglers the electronic listening device actually beeps, and only some quick improvisation by the wife (she pretends it's her child's toy that's been left switched on) averts the crisis.
 * In Criminal Minds, when the person wearing the wiretap nervously keeps moving his jacket, it caused the investigators to lose several important pieces of information.
 * One episode of Desperate Housewives had Mike putting a wire on Susan before she goes out to question Edie. The wire does not stay hidden from Edie.
 * In one episode of Spooks Danny is sent into a meeting wearing a high quality hidden microphone that works exactly as designed. Unfortunately the other people are so paranoid they take the (perfectly ordinary) stud he's wearing in his ear for a wire.
 * In one episode of Spooks Danny is sent into a meeting wearing a high quality hidden microphone that works exactly as designed. Unfortunately the other people are so paranoid they take the (perfectly ordinary) stud he's wearing in his ear for a wire.

Western Animation
"Homer: Game's up, Fat Tony! Fat Tony: How did you know? Homer: One of the ferrets was wearing a wire! (Cut to a ferret wearing a ludicrously large, beeping device that goes all the way around its chest.)"
 * Also parodied in an episode of The Simpsons, where Homer wears a very small camera hidden in a ten-gallon hat to catch Apu selling spoiled food. In a subversion, it remains functional even after Homer throws it to the ground and stomps on it.
 * Parodied later in The Simpsons, where Fat Tony and other mobsters are gluing cottonballs to ferrets so they can sell them as 'toy poodles'. Homer bursts in:

"Chief Wiggum: Fat Tony, is that you? Fat Tony?"
 * Parodied yet again, when Bart is forced to go undercover to make an illegal fireworks deal with Fat Tony. Unbeknown to Bart, Wiggum has fitted him with a two-way radio (which produces a noticeable bulge in Bart's shirt) and when Wiggum hears Fat Tony's voice, he calls to confirm it.

"Stewie: "Oh for God's sake, there's only one way to put an end to this, HE'S WEARING A WIRE!" [Various sounds of gunfire and screams follow]"
 * Parodied in Family Guy in a flashback where Stewie is kept awake by a gang of drug dealers in the motel room next door.