So what are the hallmarks of a good gadget?

• It should do something cool. Flashing lights, sound, motion.
• It should be at least marginally useful. Or as my friend Dave used to say: "Almost Useful & Mostly Harmless"
• It should be something you can't buy at the store.
• It should be a one-person project. Achievable without becoming a career. No 10-page schematics. No megabytes of source code. Somewhere around 10,000 lines of source, most any project stops being fun.