There's a company called Yoshi that does this, only they come out to you with a pump on a van. One of my neighbors uses them. I guess it works, though I never go the appeal, not to mention I'm not 100% sure how it'd work with my car, since it auto locks the fuel cap unless the fob is nearby.
When I was working at Microsoft one of the parking garages had an auto detailing place in it so you could park your car and come back to it washed, waxed, cleaned, etc.
Was a nice perk and convenient since I was going to park my car there anyway.