I've been researching dual camera (front+rear) solutions for use on my bicycle, and so far coming up frustratingly short. The most promising setup I've seen so far is the Viofo MT1 covered by Nigel here:
The Viofo MT1 is a Dual Motorcycle Dashcam, so I installed it on my bicycle, excellent results, but a few issues to note: The MT1 runs on 12 volts, 9 volts minimum, not sure what the maximum is, but probably over 24 since most hardwire kits work with 24 volt truck batteries (needs checking when...
dashcamtalk.com
However, it appears this system is brand new (still working out bugs) and not widely available at least in the USA. Power is also an issue, necessitating DIY voltage adapter for a USB power bank for bicycle use.
My rides average 2 hours with some all-day rides up to 6 hours, and I need something that will last the entire ride in both battery and recording time. Up to this point I've been using an old GoPro Hero 3+. With a 64gb card I can record the full day rides, but the internal battery only last about 90 minutes. So, I started using a USB battery pack to power the camera, which offers more than sufficient battery life for the all day rides. There is a big problem though: if the USB cable to the battery pack becomes severed or disconnected, the GoPro powers off without shutting down, and the current video file is lost. I suffered a hard crash on my bike in 2017, and the footage was lost because of this. So, this setup will be of no use in the event of an accident.
I thought of switching from the GoPro to an actual dashcam, powered with a USB battery pack, would be a good solution. But, the issue is that it appears that few if any of these can be natively powered via USB without some type of complicated DIY voltage regulator/adapter. Then there is the issue of weatherproofing, car cameras are not suitable at all for outside use.
The issue of loop recording is not as important with a bike camera. While loop recording would be nice, to me it's not a big deal to simply format the card before every ride. So in that sense, two older model GoPros would work fine for me if I could solve the USB power cutoff vulnerability.
I've looked at the purpose-built bicycle cams (like the Cycliq), but in all truthfulness the high number of negative reviews and problems reported for all of those has made me shy away from them. Hoping for some insights here.