So you live in a big city like say, San Francisco and you don’t need a car everyday. But when you need a car, you really need a car. And you’d rather not drive the Hyundai with 9,247 miles on it they have at Avis. Audi is coming to the rescue with a new car sharing service called Audi on Demand.

The concept is simple, Audi has a fleet of cars in your city – right now the only city it’s available in is San Francisco – and they have an iOS app. You have a credit card, a valid driver’s license and an iPhone. All you have to do is download the app, pick your dates, select the model Audi you want to drive, enter your info and, boom, Audi brings the car to you at the time and place you specify. If you don’t have an iPhone, don’t worry. We’ve been told an Android app is in the works and you should be able to register and reserve an Audi online at www.audiondemand.com soon as well.

And just about every model is available for use. Got a hot date you want to impress, reserve a R8 Spyder for the evening. Want to take the family up to Mammoth for a ski weekend? Book an allroad or a Q5. You can reserve a car up to six months in advance or as little as two hours ahead of time. The Audi Concierge will bring the car to you or you can pick it up at an Audi Concierge garage. You can rent the car for as little as one day up to 28 days.

Prices start at $155 per day for an A4 and go up to $1,285 per day for an RS8 V10 Spyder. There is no membership fee and all vehicles feature quattro all-wheel drive, Sirius satellite radio, navigation and premium plus trim.

We expect Audi on Demand to be available in other high-density metros once the service is successfully launched in the Bay Area. Audi is also looking at launching a premium collaborative ownership program called Audi at Home in upscale condominium complexes that would allow owners to share an exclusive fleet of vehicles.