Yes, it's possible... and it can record with the phone turned off (in many cases) if the battery hasn't been removed. Calls can be recorded and it can operate as a remote micropone so that background conversations are picked up.
You weren't specific about the carrier, which will be part of what determines the answer. FlexiSpy is one option, but again it will depend on carrier and the type of wireless network they have. Also if the phone is turned off but recordings take place, you may have to wait for the wireless mode to be turned back on.
Most importantly, you could be considering something that could break many laws. I'm not a lawyer, but unless you know for certain that it's legal I would hold off until you research the legalities more. If you think someone has illegally used something like this against you, you should contact law enforcement and your wireless carrier.
As long as the person on the other end of the call knows you're recording it is legal. Otherwise, it isn't. Unless you have an official reason to be listening. Aka, a warrant, or work in homeland security, in that case no one really knows what the rules are, or if there are any to begin with.
Posted from my CrackBerry at wapforums.crackberry.com
