Before smartwatches, there was the gesture-controlled, touchscreen Casio AT-552 Janus. That’s right, the AT Janus models (AT-551 and AT-552) included an eight-digit touchscreen calculator where the entire display could be used to ‘write’ the number or calculator function. The watch would recognize what had been written by the user’s fingertip and perform the calculation. Read more for the full demo video.
“The downside? Sometimes they break. Usually it’s the analog portion that stops working (and these are a nightmare to disassemble, I wouldn’t recommend it unless you know what you’re doing). I’ve transplanted pieces between like AT models with great success and, theoretically, you could replace the analog with one of the more generic analog/digital Casio units (which are much cheaper) but I haven’t tried this so am only guessing,” according to Liquid Crystal NZ.