I’ve been playing around with Android application development quite a bit, over the last few months. The one thing I’ve built that’s actually quite usable has been the wake-on-lan client Etherwaker (because the world really needed another one of these, didn’t it?)
I’ve just put the Mercurial repository for it up on Bitbucket and released it under the GPL-3, for people to peruse or fork at their leisure.
Five second guide to fetching the source: hg clone ssh://firstname.lastname@example.org/pdwerryhouse/etherwaker
If you can’t be bothered with all this, and just want to wake up your mythtv box from your bed, then it can be downloaded from the Android market.