Would you rather it happen automatically or after you give a voice command such as "Shower On" or something similar? Having the water pre-heat would be very cool. The problem would be knowing when to start heating the water. Assuming the home owner doesn't follow a perfect schedule, a voice command would be the most effective. Another possible solution is that the water starts heating when you enter the bathroom. Motion detection isn't that difficult, so the latter might actually be the better solution. It would depend on how long it takes to heat the water to the desired temperature.