Foursquare on your wrist! I am a Foursquare addict, I love using it to find new places and am constantly checking in to keep the recommendations current. There are a few apps on Android/iOS that make the process of checking in painfully easy and incredibly fast (Simple Checkin/Checkie/etc). I took that concept and shrunk it down a little bit, now you don't even have to get out your phone (well, on Android you do...for now...the Javascript won't run unless the app is in the foreground). Take a peek at the source code, give the app a try, I'm using location, local storage (for auth token), and http requests to the Foursquare API.
Authentication of the app is done through the native Pebble app using the "configuration" gear, log into your Foursquare account and authorize Spoon, and you should be good to go!
I've been working on this since SDK2 was released. I finally have it in a form that is usable, though I don't think I can do more until the Beta3 or the final Pebble 2.0 ships. I leave it here for you fellow Pebblers to do your worst and let me know how terrible my app is. :)