Groupon offers the Peak Wireless Rearview Mirror Camera System, model no. PKC0RG, for $79.99 with free shipping. That's the lowest total price we could find by $20, although we saw it for $6 less (with rebate hassles) two years ago. It mounts to a car's license plate and features a built-in 3.5" monitor, weatherproof wideview swivel camera, standby mode, and more. Deal ends July 21.

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