I've only had a person come up on me like that a few times, most of the times I just gunned it (fortunate timing). Then again my 225hp Grand Prix had a little better speed off the line than my MB does.
I haven't really started looking yet blacksmoke, if I go with the third brake light I'll use LEDs and put it at the top of the rear window. I don't know of any that would directly fit out cars.