Having a look around online for images of old calculators of course lead to photos of Casio calculator watches, and that triggered this vague memory I had of seeing a Casio watch while on holiday in Tenerife which could transmit to FM radio. I suspect that would be technically illegal here as you'd need a licence to transmit in the UK (a pirate radio station on your wrist!).
I always wondered if it was one of those things where I 'misremembered' something (it would've been a very long time ago), but a quick search brought this up, so it must've been this watch that I saw. It's nice to know I'm not going crazy. Well, maybe I still am, but this bad boy definitely existed!
