Colin_P
Guru
Already out there, as a "wearable device". Just battery life is somewhat limited.
Compare say a Nokia 3310 and any of the current smartphones
Battery was replacable, now sealed in.
Battery life between charges, days now a day. Smaller battery, but more is being asked of it, so it doesn't last as long.
Solve that last part first, before placing any electronic system into a bike build.
I'm not thinking of a wearable device although a transponder that car collision avoidance systems could see could easily fit in one, I'm thinking more along the lines of the current fancy pants garmin bike lights that adjust their brightness as a vehicle approaches you and also provides a proximity display on the gps unit screen.
I don't think battery life will be an issue as batteries are likely to get better and as now you'd recharge your lights / garmin before a ride.
Thinking some more about a safety system such as this, it could put an almost immediate end and greatly reduce (obviously older vehicles wouldn't have it) cyclist death and injuries due to vehicle collision and the best bit would be most of the tech would be in the vehicles. It would only require a minor tweak to what many cars have already in the way of collision avoidance systems. Currently many cars have lane assistance, they can self park, they have backup cameras, they will apply the brakes in the event of an imminent collision etc.