Aftermarket Safety System Mobileye 560 Reviewed by Consumer Reports [Video]
Consumer Reports says they might have found a cheaper solution in the retrofitted Mobileye 560 system, which can be retrofitted to just about any car. The system uses a camera which you'll have to stick to the windshield under the mirror.
The device is rather steep though, at $850, but does come with things like lane departure warning, collision warning and even detects pedestrians.
However, since it doesn't have that all important blind spot detection and can't actually brake the car for you, we think this is just a glorified beeper not worth the thousand dollars if you include professional installment.