I heard about this on the radio this morning during my brutal commute to work.
...I was vastly unimpressed by the GM rep who was touting this as "amazing". I think V2V communications will become very good and important, but they need a new voice for it (this guy was a giant turd).
Also, introducing it on one model as an "available" feature = "spend lots of money on this safety feature that is limited unless you're about to rear-end another Cadillac CTS."
...and when introduced on future models, it'll probably be modified with no ability to upgrade the original on the CTS.
It shouldn't be "optional" on the CTS if they plan on introducing it - it should be standard on all redesigned GM vehicles, and capable of cross-manufacturer use (i.e. Caddy can speak to BMW, etc.).