I saw them on CNN earlier. They reported that they are expected to go nationwide by 2020.
It's a neat idea but I'm not seeing it actually being feasible. Besides the security aspect, how are they expecting to power them on current vehicles? Batteries? Require the owners to take them in every night and charge them up? I can see them being required on future vehicles that have a wiring harness built in and designed for it, but for older vehicles I don't think so.