Article: FBI taps cell phone mic as eavesdropping tool
Can this be done with a symbian phone?
So can the FBI use my phone as a mic?
Not unless you let them install some sort of surveillance software on your phone. They can, of course, listen to any conversations you have, from recording the radio traffic, or directly tapping into the operator's systems, if they want to ( and since you posted here and questioned this in public, they're already on to you. 😉 ).
Or just fool your phone to think that the handsfree is connected, activate auto-answer and simply call that phone (obviously on silent, without vibrate)