Approximal is an iOS app that uses Bluetooth to discover people nearby. It can match you using social networks (18 supported so far, including the usual suspects), or any adhoc personal networks you and other people create. [more inside]
I was playing round with Google's Fusion Tables and suddenly realised that it was both a map tile server and also a spatial query processor, all for free! Had previously struggled setting up PostGIS and Tilestache, so this was quite an eye-opener. Made a little test project, showing most of the gym locations in the UK, which shows the nearest five gyms for any other gym and also has Street View captures for a small subset of them.