There is nice service in the US with cars and an iPhone app.
Their goal is that you’ll use UberCab when you need a car service.
If you want to use it yo can use your iPhone app or SMS to request a black car limo service within a matter of minutes, for about 1.5x the cost of a taxi, with one click iPhone requests, with location based dispatch, with on demand limo service and in app billing – no cash needed.
Take a look at the video. It is quite an idea.