Moreover, the whole 'smart bathroom' thing has already been pretty much solved in Japan - and more or less keeping in mind the principle that you describe. You

Moreover, the whole 'smart bathroom' thing has already been pretty much solved in Japan - and more or less keeping in mind the principle that you describe. You can get your temperature, get a warm seat, turn on some ambient music to mask your own, more personal music, flush, bidet, whatever all in most toilets in your average department store. You can get more complex offerings that do perform some more complicated tests if you really want to. The 'bath room' itself is also typically a single, self contained unit, often in some kind of mold, and including the shower, accoutrements, and bath in a full space designed to get wet and save/share the clean water in the bath. The 'bath room' usually has a waterproof, electronic control panel which allows you to set timers for filling the bath, set an ambient temperature to keep it at, set the preferred level of water, set different default temperatures for the shower and bath, and typically also access all these features from other places like the kitchen where a companion panel is installed. This is typical of your average house - I just described my wife's parents' place, which was built 10 years ago. The whole design thing is completely solved there, and why that approach has not been adopted across the U.S. and Europe by now is completely beyond me. But the killer thing there would be to bring the Japanese approach to the US and Europe and plug in some better smart access features. Or go to Japan and plug them in there, where the infrastructure and demand is already in place [well, Google is probably on it already but...]