Back in the good ol’ days there was a toy called the GirlTech IMME, which had a sub-GHz radio chip, a display, and a keypad. It was bulky and heavy, but good folks had a lot of run writing radio exploits for it. In a fit of nostalgia for those days, I cloned the Casio 3208 calculator wristwatch module with the CC430F6137 chip, giving me a better CPU than the IMME but essentially the same radio. It runs for years on a coin cell battery, and in addition to the radio, RPN calculator, and hex editor, it just happens to tell the time.