Rydeen is shipping its rear view back-up system called the N series. It automatically starts beeping when the vehicle gets close to an object. The system uses sonar, not a camera, but you can add a camera feed for double security. It automatically activates when you go into reverse gear.
The N2 is a dual sensor package for $100 MSRP and the N4 has four sensors at $140.
Source: Rydeen
