Found this a while ago:
http://www.theaircar.comIt almost sounds too good to be true, but reading through the website it could be a possible top-seller. Especially in the big cities I think.
I wouldn't buy one since I drive too much for my work to make this a good alternative, but if I live in a city with everything close by, I'd might buy one if the price was right (and when it's available of course).
Would you?
