Does it do the same like the Dietz 1250?
What are the differentses?

(or does this one gives a menu item on the nav screen?)

I just installed this exact system in my MINI Cooper (i.e. NavTool). It works great and is very easy to install. It comes with a plug-n-play wiring harness that is made for your specific vehicle and requires a +12v accessory power wire plus a ground wire to power it. The seller (i.e. cardemand) is great to deal with and has 100% positive feedback on eBay. He also has a small website for his NavTool products here:

http://www.navtool.net

On his web site you can download a PDF document showing all the vehicles he makes his NavTool unit for.

The NavTool unit is very solid and well made (with a small metal case). Definitely worth the $199 asking price (especially since it's half the price of the Dietz!!!). I really like mine.

BTW, there is no menu on the nav screen. It is simply a video input and nothing more. It includes a small switch that you flip to turn on the video input when desired. There's also a second video input that can be used with a rear-view camera if desired. It can be auto switched via a +12v signal from your brake lights. Best of all, the unit supports video-in-motion. It has a wire that is supposed to go to your hand brake (to prevent the unit from working when the hand brake is released), but all you have to do is run it to ground and then it fully supports video-in-motion.