Burn Notice2007

Michael Westen:
[narrative] Contact microphones pick up sound vibrating through walls, allowing you to eavesdrop on conversations. Pair one with a little wireless transmitter and you have a bugging device that doesn't need to be in the same room as your target... Of course, bugging a room from the outside makes it impossible to see potential pitfalls. Just as a cellphone reacts when it's placed too close to your alarm clock, a room full of speakers can create radio frequency interference if you're spying on someone with a wireless signal.