🤔 The circuitry inside a Casio watch isn't too complex, maybe I could measure it and manufacture a replacement with more features.
Oops somebody already did it! Way better than I would have!
The "Pluto" watch, which re-purposes the case and LCD from a Casio F91-W, includes a compass, infrared programming, RTTTL ringtone (musical) alarms, generates RFC 6238 one-time passwords, open source, and runs for a year on a standard watch battery! Wow!! 😮