Something like this should work with a Hero 4, just make sure the one you get works with the GoPro you have. You plug this adapter into the heli plug and your own headset into the female connection on the adapter and it picks up everything running through the comms when you plug the mini-USB into the GoPro to record. If you get a version with a heli plug it will be a lot less work to fit the setup in an R22. I used to attach the GoPro to the RH headset hangar in the R22 and it captured the whole instrument panel and outside cockpit view, very useful for debriefing after the instructional flight as well.