With the PCB fabrication services available to the modern hobbyist, it’s become increasingly common to see replacement boards designed for all sorts of devices. Even so, it’s sometimes still a little difficult to believe that we’re at the point where hardware hackers are now producing advanced replacement PCBs for commercial wristwatches such as this drop-in upgrade for the iconic Casio G-Shock by [David Volovskiy].

Honestly, we’d have been impressed if the thing could just tell the time. But the replacement board combined with the open source firmware brings new capabilities that far exceed anything the G-Shock was capable of originally. The upgraded watch now offers several applications, such as a pedometer and a number of games including simplified versions of Blackjack and Wordle. The watch can tell you the phase of the Moon, calculate sunrise and sunset, and display values pulled from the internal thermometer.

Even if you don’t have a G-Shock in need of a new PCB, [David] has put together a web-based emulator that lets you play around with the firmware. The online tool that lets you visualize how the watch’s LCD is mapped is also very slick. For those interested in getting a board of their own, you can join the project’s Discord server and get your name on the list for an upcoming production run.

If some of this sounds familiar, it’s because [David] based his project on [Joey Castillo]’s Sensor Watch, which is a replacement PCB for the Casio F-91W. With these two projects available for others to build from, one wonders how many other Casio watches might get their own upgraded hardware in the future.