We present 64Key, a hardware/software platform that enables impromptu sensing, data sharing, collaborative working, and social networking among physically co-located users independently of their own hardware platform, operating system, network stack, and of the availability of Internet access. 64Key caters to those scenarios such as computer labs, large conferences, and emergency situations where the network infrastructure is limited in operation or simply not available, and peer-to-peer interactions are prevented or not possible. By plugging a 64Key device in one’s mobile device USB port, an independent network is created on the fly, which users access from their own device though a web-based interface. In addition to default apps such as chat, file sharing, and collaborative text editing, 64Key’s functionality may be extended through the run-time installation of third-party apps, available at a public app store. We demonstrate our proof-of-concept implementation of 64Key with multiple apps in a set of key scenarios.