We just had a new light switch installed in our bathroom, the Lutron Maestro Occupancy Sensor. It is smart and cool, but it needs a user manual! Yes, a manual for a light switch!
Because of new building codes, bathroom gear needs to conserve energy by keeping electricity use to a minimum. One way of low use is via LED lights; the other is via a smart switch that has a motion detector built in, which will fade the lights after X minutes if no one moving inside. And it will turn them on when you enter. It also remembers what level the light was last when you turn it on. The downside is that you have to PROGRAM the light switch — what levels, when, and how long it takes to go off. It comes with a dense how-to-manual. But the default settings seem fine and the device is pretty cool. Here is a shot of the instructions, which also cover the other side of the paper.
It costs about $36 from places like Amazon.