Have you been watching the market for any possible rechargeable replacement for your coin cell? Also, is there a possibility of underdriving those LEDs to conserve power a little while still retaining visibility? The revision I'd like to imagine would ditch BLE but add USB for charging and/or syncing with a PC. Given that there are a lot of platforms to choose that run Espruino this might be relatively trivial to code (leaving the hard/fun part of the physical design). Please keep revising!

Hey, sorry for the +1 year reply lol. Your ideas are all very good, but I'm not sure if I have enough skill to fit a full USB charging circuit on the watch. Also, I think a lipo might be too big/thick for the watch. I was thinking maybe just add a small lipo battery with around ~2 days of battery life, and a charging cradle/dock thingy that has all the support circuitry for charging. Also, I love your idea of USB but I have very limited experience with it and some of my USB projects have failed and I have yet to know why. I'm not sure when I'll make a new revision as I'm very happy with the current version, but I'll keep your ideas in mind for sure when I start working on one!