I'd think you are going to pay a pretty hefty premium for the convenience. Remember a lot of these are designed for commercial use where water temperature is pre-set but there are ones you can adjust the temperature. There are battery, low voltage, and even solar models available.

Here is a link that might be useful: Sloan Solis Faucet

Or you can go this route and not worry about batteries or electronics. You change the water just like always but you'll find, no matter which type hands free device you use, that the need to change water temp is much less than you'd ever think. I have two. The one in the kitchen has been there since 2002. Bathroom, 2007. Without a doubt the #1 most favorite thing of the kitchen remodel!

Here is a link that might be useful: Tapmaster Hands Free Water