The reviewer said he can drive at highway speed in his convertible:

I took the 'stang (and the new Jawbone) for a top-down spin on New Jersey's incredibly noisy highways. The results were really amazing: even travelling at 65mph, surrounded by cars, SUVs and 18-wheelers, I was able to hear my callers quite well; and, they could hear me perfectly.

I'm sure it will work well in my car, as well…I can barely hear people and they can hardly hear me, with the top up, in the city. I might have to pick one up. Gold, black, or silver? Probably black.