I need a voice activity detection module (VAD) for my wearable computer. Should I roll my own, or use someone else's (open-source). My immediate need is speaker-dependent (just me), but it would be nice if I could offer up a speaker-independent version eventually.

Check out this one: https://github.com/wiseman/py-webrtcvad

If this one does not work for your application, perhaps look into simpler ones like the ones used in mobile telephone codecs or in Speex.