I rarely leave the house without my Fly6 on whatever bike I'm on. It's very easy to switch across bikes and it is a very decent rear light aside from the camera feature. I have however needed the footage twice maybe but has also caught good 'happy' footage of out with friends and family. I also have the Fly 12 front but rarely use it as it's harder to move across bikes, isn't as useful as a light and is big and heavy.
Aside from that I have ETC camera, chilli tech cam and had an apeman and mobius. The latter two wouldn't be a recommendation, the ETC is ok for something cheap and nasty (it looks and feels that way and isn't as user friendly as the Fly's) and the chilli has a short battery life, is quite heavy and footage isn't great. I have it mounted on my Enduro helmet for when I take that bike/helmet combo out.
Aside from that I have ETC camera, chilli tech cam and had an apeman and mobius. The latter two wouldn't be a recommendation, the ETC is ok for something cheap and nasty (it looks and feels that way and isn't as user friendly as the Fly's) and the chilli has a short battery life, is quite heavy and footage isn't great. I have it mounted on my Enduro helmet for when I take that bike/helmet combo out.