There's the Misfit Flash ($12-$20) which should work with Beeminder:
Automatically tracks steps, distance, calories, and light and restful sleep
Splashproof (not swimproof) disc with red LED progress and time display
Smart button enabled to control connected household devices
Wirelessly syncs with paired smartphone to upload data
Non-charging, replaceable battery lasts up to 6 months
Also includes a clasp, so I think it should work in a pocket.
There's also the Fitbit Zip which is similar and uses a "watch battery that lasts up to 6 months". Looks like it's much more expensive than the Flash though.