I'm not sure if this is even coffee related, or just simply food related, but surely someone will think of a coffee application for this: http://www.sousvideathome.com.au/
Basically it's a PID to keep temperature at a solid temperature for a period of time using a basic rice cooker, but almost anything could be plugged into it with a heat source. Even plugging into a kettle to keep water at a perfect temperature for pourover.