Streaming sensor data from dynamically reprogrammable tasks running on mobile devices

We describe Flux, a platform for dynamically reconfigurable data sensing using mobile devices, like smartphones or tablets. Periodic sensing tasks are programmed using the Flux Task Language and compiled onto abstract byte-code that is executed by a low-footprint virtual machine, guaranteeing by construction important runtime safety properties. For task dissemination, a Flux gateway performs on-the-fly injection of tasks on devices present in a geographical region, and sensing data is streamed back to the gateway that forwards it to a publish/subscribe broker. Live or archived streams are in turn fed by the broker to data processing clients. We implemented a prototype of Flux and used it to conduct a case-study experiment where the intensity of Wifi signal in our department is measured over a certain survey area, using smartphones and tablets carried by volunteers as they walked over the survey area.