I would also say that a rear facing under seat camera would be beneficial on a cycle as no doubt, this shows what happened in the lead upto an event such as reckless/impatient/dangerous driving and a helmet camera would be best to capture from the side/infront, giving a better perspective of what the rider see's.
I have a rear facing YI (go pro style) on my motorbike and it does help to act a bit of a deterrent. It also caught a classic clip of a taxi that assumed I would jump an amber/red light, when in fact I did what we should and slow to stop. I just head screeching tyres behind me. When I reviewed the footage at home, it was lucky the taxi driver didn't hit me as he began to nail it as I started to slow and he was almost tailgaiting. Lots of other stuff captured such as being startled as a vehicle appears out of nowhere on the motorway, only to see from the rear camera its been swerving across several motorways lanes without slowing, far quicker than 70mph traffic darting through since it comes into/out of view from both front/rear cameras.