Personally I've always been a shower guy, but this Starfish Bath Sensor may make me switch it up once in a while, if I could get past the "soaking in my own filth" aspect. The Starfish has a water sensor so you can let your bath water go while you're getting your bubbles, music, and booze ready for a long soak. When the water level rises to hit the Starfish, it'll notify you via a sound—do starfish make sounds?
Also, the temperature sensor tells you exactly what the water temperature is, preventing you from burning your delicates. The Starfish is powered by 2 AAA batteries, and you can pick one up for $17.99.
Product Page [Whatever Works via Gearlog]