For several years millions have shared the places they've been using the Where I've Been website and Facebook application. The site also has an API (our Where I've Been API profile), which allows for much of the same functionality, such as searching countries, marking it visited and adding content such as a story or photo.
Services like Find My iPhone and Where’s My Droid have been helping people relax for years. The relief that comes from knowing where your phone is and being able to lock it until you get there is amazing. However, what if you lose a device that does not connect to cellular networks, like most laptops. That is where PlaceEngine and the PlaceEngine API come in.
PubSubHubbub. Say that three times fast. If you're not familiar with PubSubHubbub, it's an extension of the RSS and Atom protocol that allows the feed to push content out when it's updated. That's just the sort of technology we should see from check-in APIs like Foursquare and Gowalla.