I agree that it would be great for rental cars or people new to an area. Not sure why it has to be a robot, though. What if I wanted to make use of a variation of the technology that would aid walking, biking and using public transit? I wouldn't want to lug it around. Perhaps they could add legs and it could walk around with you and carry your stuff. That would be innovative.
Hong Kong - Stacked like lab animals!
http://www.boingboing.net/2009/11/20/photographs-of-resid.html
MIT's AIDA Robot Is Going To Be The Ultimate Backseat Driver