Get a hands-free kit and it should be very easy to splice the earpiece feed.

 

Federal law allows one person of the conversation be aware of the recording....I asked the FBI this once..

However, since you are broadcasting a radio signal can't you listen to it on scanners...Therefore can't you record what you hear? I do not know the answer to that. But I remember an incident when a couple were recording scanner conversations on cell phones and were able to get Newt's cell phone conversation.. I do not believe they were punished..