It's only a part answer, but people who are into cars certainly do screw around in a similar way, whether just to read diagnostics codes out or going full out and remapping the ECU for extra performance/efficiency/whatever they want. There are even hacks to change throttle response now.
My microwave, on the other hand, I'm not sure there's much else I want it to do that I'd consider reprogramming it for ;-)
Microwave... Just a wild idea off the top of my head: coupled with hardware hacks, like, some sort of IR pyrometer it could actually adapt output to maintain the food heated at specified level or just turn off when a certain temperature is reached.
My microwave, on the other hand, I'm not sure there's much else I want it to do that I'd consider reprogramming it for ;-)