I have and use a Sena 10C. It's a helmet cam, comm device, bluetooth device. Shoots max res at 1080 @ 30FPS. That's fine for most of what I am doing. Couple things I have found now after 3 years is that the battery life is really starting to get shorter and shorter. Also, the setup and rotation of the camera is a pain - there's no live view.
There is a new camera Sena has out, and it is a serious contender for me. It allows live view (making alignment easy), higher framerate, better battery life and (HUGE) you can charge while using it!
Other cameras I am considering are the Sena Prism Tube, GoPro Hero 7 Black, GoPro Session (referb, but cant beat the size). there's others, but those are the contenders for me.
I would also suggest heading to the following site - it's all they do. Motovlog - The first Moto Vlogging Community