Here’s another one of those “why hasn’t this been around before?” moments. For your bathtub, this plug has a pink flower attached to it, a flower whose color changes in response to the temperature of the water. When the water reaches a sufficiently warm/not-too-hot temperature, the flower turns purple. Purple flower = bath time, simple as that.
The odds of you being able to walk in a Wal-Mart and buy this are pretty low I’d imagine. Guess you’ll have to be satisfied with low, low prices on other, non-“wow-good-idea” items.
A Flower To Test The Waters [Yanko Design]