I was at a hospital today... not much fun. Anyway, I noticed that they had little signs posted up saying to constantly wash your hands or use that alcohol-based cleaner. Near the sink in the room I was waiting in was a sign that said to leave the water running while washing, rinsing, and drying your hands (then turn it off with a paper towel) so as not to touch the tap with clean hands.
So, I figured that there had to be a better - and less wasteful - way to do it. The best idea I came up with in that short moment there was having a foot pedal, or perhaps two:
The one on the left would stay where it is put, and would control the temperature, leaning side to side. The other one is viewed from a side angle, but it would be more like an accelerator, controlling the flow of the water. Granted, this would be pretty complicated and quite unnecessary, but I still thought it was an interesting idea.