I just released on Github the PHP code I used on my Raspberry Pi (and now a remotely hosted website) to respond to Lockitron API Webhooks and issue commands to my Lockitron (in this case to lock the Lockitron 105 seconds after it unlocks).
It's real basic but lays the groundwork to do more. Feel free Fork it or issue Pull requests or ask me questions.
I'm using this PHP class as well as a MySQL server to register iOS devices for push notifications, notify apps about information received from webhooks, and issue commands to Lockitrons that can't be issued directly from the iPhone (ex. a delayed lock command).
P.S. If anyone wants to help me develop this Lockitron iPhone app I'm working on feel free to PM me. I love to write code but hate coming up with feature ideas or spending time on the UI.