The dish-o-tron 6000 is a thing of beauty by the hacker Blondihacks. It is an automatic dishwasher monitor built to detect if a dishwasher contains clean or dirty dishes. The beauty lays in the fact that it does that by simply hanging on the outside of the machine. No warranty voiding on expensive kitchen equipment involved.
When reading about it, make sure to catch the rev B part as well. Some subtle improvements such as removing the battery dependency as well as general stability fixes are applied.