During the course of a seminar two friends and I realized a location based service on our own as a proof of concept.
Our goal was to unify offline and many online identities by having users interact via a map on their iPhones.
I developed the server infrastructure by expanding the XMPP server OpenFire with custom implementations of several XEPs. I used Wokkel which uses Twisted to provide a testing ground for XMPP.
You can find more details in the paper.
The source if available under the MIT License here.