In our review of the Pebble SmartWatch, we only had two complaints about the software: a lack of apps, and a lack of utility. The second point stems from the fact that the Pebble can only receive alerts from your phone, and it can't send information back. Both issues have now been addressed by the Pebble SDK. Developers have been cranking away on watch apps for some time, but the latest SDK update adds AppMessage, a method of implementing bi-directional communication for Pebble. Translation: your watch can now tell your phone to do stuff.
Of course, support for this feature will require Android app developers to either bake it into their existing apps, or create a bridge application, plus the official Pebble app.