I recently presented at the conference Boundaries, Frontiers & Gatekeepers on some of my Foursquare research.
I've embedded this as a Slideshare presentation. It doesn't offer an elegant way to display the speaker notes so I had to include them as comments (if anyone knows a better way, please let me know). To view my notes, you'll need to click to Slideshare's website.
My research on location-based services, georeferencing, and mobile applications is still in the very early stages, but this presentation gives a sense of the area of my exploration.