I don't think this is exactly what you're looking for, but my favorite repurposing of old devices was when I was looking for something to do with the eight Kaypro IIs I had kicking around about 15 years ago.

What I ended up doing was chaining them together to use as a single multiprocessor PC. Those 8, working together, came very close to reaching the same performance as a low-end "modern" PC of the time.