FBI turns on cell phone microphone remotely.

"Nextel and Samsung handsets and the Motorola Razr are especially
vulnerable to software downloads that activate their microphones, said
James Atkinson, a counter-surveillance consultant who has worked closely
with government agencies. "They can be remotely accessed and made to
transmit room audio all the time," he said. "You can do that without
having physical access to the phone.""

http://www.schneier.com/blog/archives/2006/12/remotely_eavesd_1.html