The Priceline Negotiator app for the iPhone has been updated to include car rentals. Users can negotiate their own prices as little as 30 minutes before pickup, with savings of up to 40 percent off regular rates. The service works with five of the leading car rental agencies: Alamo, Avis, Budget, Hertz, and National.

When starting the app, users choose the type of car they want to reserve, including economy, compact, mid-size, full size, luxury, convertible, minivan, and SUV. The app includes winning bid recommendations, so users can see the recent winning bids at the same airport, ensuring a greater chance of money-saving success.

The checkout process has been simplified so that it only takes one screen to finish the process. Users will know instantly if their bid has been accepted, and will immediately receive  their rental details and pickup counter location.

The same app also includes a Hotel Radar feature, which lets users point their phone in a particular direction to see available hotels, along with published rates and distances. Users can book immediately online, or call Priceline directly to make a reservation.

The Priceline Negotiator app is a free download for iPhone and iPod Touch in the Apple App Store.