Citysense is a location-based social network of a different breed. Rather than interacting through the network through a Web portal, Citysense lives as a mobile application on your smart phone. Currently, only BlackBerry users can take advantage of the service, but an iPhone application isn't far behind. Rather having a friend feed, Citysense populates a map of where people are transmitting a cell phone signal from. You can see where your friends, called tribes, are congregating and instantly get information about what's happening at a local hot spot.