The original band for my Pebble watch snapped in half on the hole side due to fatigue, and after a year or so the replacement band (which was made of a relatively stiff plastic) was about to do the same thing.
Since I'd recently acquired some flexible filament (Maker Geeks Maker Flex TPEE), and didn't feel like wasting ~$10 to buy another full watch band, I decided to just model and print my own version of the one that was failing. I reused the existing spring-loaded retaining pin.
The resulting part was considerably more flexible than the one it replaced, and showed no signs of wearing out after a full year of daily use. As my filament is Candy Apple Red rather than black, it doesn't really match the rest of the watch, but I don't care.
Edit: The original model was 21.00 mm wide where the pin connects it to the body of the watch. It kept popping loose on me, so I definitely recommend a larger width (at least for the pebble). I made a wider version (21.75 mm), but I didn't get around to printing it for testing until recently. I have used it without issue for a few weeks now, but there's also an untested 21.50 mm version, if you'd prefer the pin to be a bit easier to retract.
Printed at 215 C with the heated bed at 65 C. My printer is modified with Thing #134811 (to allow easier/faster flexible filament printing) and a glass bed. My usual go-to of hairspray on the glass bed doesn't seem to work very well with this filament. Purple glue stick works much better.