Today I'm wearing a watch with it's place in history - it was Casio's first pressure sensor watch.
The watch is a BM-100WJ and was released in February 1989. It has a semiconductor barometer sensor which periodically measures the pressure. It uses the sensor in several ways;
1) It could predict the weather based on whether the atmospheric pressure was increasing or decreasing, and high or low.
2) It equated the pressure to an altitude so it can measure hoe high you've climbed.
3) It could also be used for diving with a depth measurement based on the pressure increase as you go deeper.
The watch sold well and Casio followed it up with all manner of sensor watches. This combination of both altitude and depth is still unusual though, and I can't think of any others with the same combination.
The watch uses a 560 module, has other modes apart from the sensors. It also has alarm, timer, and stopwatch. The display is a 2 line LCD screen with day, month, and date along the top, and time along the bottom. There are also other markings along the left side for the pressure trends.