The team behind the Pebble smartwatch released a "proof-of-concept" SDK last week, letting developers create their own watch faces and rudimentary apps. A few are already available on the Pebble forums, but the most impressive so far is a surprisingly playable version of Tetris. Once you get your head around pressing down to move right and up to move left, it's almost like you have a miniature Game Boy with a slightly better screen on your wrist. Installing Pebblis is a simple matter of clicking a download link on your phone, at least if you're using your Pebble with an Android device — iPhone owners will need to wait for an official app update, however, or try a direct Bluetooth workaround.