Quickly get the days since our last SSL incident (such as Heartbleed) from dayswithoutansslexploit.com

Using WristHQ, and a Pinoccio microcontroller, you can easily connect two pieces of startup hardware together. Using the Pebble, you can modify most of the Pinoccio's pin settings, and change the onboard LED quickly. 

A fun project is to create your own color changing light bulb using an RGB LED + a opaque enclosure to create a disbursement of color, controllable by your watch.