TinCan is a one-to-many text messaging app that doesn't use the internet or cellular service. Instead, messages hop from phone to phone over WiFi tethering. TinCan is normally a very inefficient messaging platform. However, it should work well in populated areas such as a festival, conference, or similar gathering. As TinCan doesn't use the internet or cellular service, it could be useful where these services are lost, as in a natural distaster, or blocked, as in a protest. (Via hubski.com.)