The Garmin GTR200 has built in 2 place intercom which is a nice combination for VFR panels. There are other similar combinations from Garmin and other manufacturers. the GTR200 has separate PTT inputs for pilot and co-pilot. Pushing the co-pilot PTT button and talking into the pilot mic will transmit nothing. I haven't tried it, but I'd think one has to over ride the other when both buttons are pushed at the same time. On the other hand it could be that both mics are active. The Pilot Guide doesn't specify.

If you have an audio panel, the GTR200 intercom can (must) be turned off, but the PTT buttons are still discrete and need to be wired separately. That would allow the pilot and copilot to control different radios through the audio panel.