Things I thought of while in the tub

Why don't they make a device for your bathroom that shows you when your hot water heater is done doing its thing? If you had that, you wouldn't turn the water on until it was ready (premature hot water requests slow down the heater, don't they?).

There should be a thing like a poncho with snaps around the border that you could attach to the tub to make a warm air tent. It could be made of two layers of stretchy terry cloth separated by a thin flexible layer of plastic and have hand holes. It would keep cold air out, warm air in, and would enable book-safe bathtub reading. They could market different shapes: rectangle, round, and oval; they you would pick the best match based on the tub. The snaps would attach to the tub with some sort of water-proof, but non-permanent adhesive, so that you could move them if you weren't happy with their placement.