In the UK they have an acronym that covers most accidents: SMIDSY, or "sorry mate, I didn't see you". It's pretty common, and now Volvo is out to do something about it; It has teamed up with Ericsson and Swedish helmet maker POC to make a helmet that connects via Bluetooth to your smart phone, which then broadcasts your position to Volvos that have connectivity built in as a standard feature.
Klas Bendrik, VP and group CIO at Volvo Cars, is quoted in Wareables:
...by exploring cloud-based safety systems, we are getting ever closer to eliminating the remaining blind spots between cars and cyclists and by that avoid collisions.
Of course when you watch the video, you don't see the car stopping to allow the cyclist to continue pedalling safely; you see the cyclist get a signal and some flashing lights that tell him that there is a Volvo coming. There also is only once cyclist on the sidestreet with no other moving cars; in any city with a decent number of things to ping that helmet would be ringing and buzzing nonstop.
I might have considered this helmet if it showed the cyclist getting priority and the car stopping. Instead it gives the car priority, putting the burden of responsibility on the cyclist. And of course, instead of SMIDSY, we will soon have SMYWWSH or "Sorry mate, you weren't wearing a smart helmet."