MELOS: a low-cost and low-energy generic sensing attachment for mobile phones

Ubiquitous availability of cellular network and cheap mobile phones have made them promising sensing platforms for various application domains including healthcare, environment, and astronomy among others. However, existing mobile phone platforms, including even smartphones, provide limited in-built sensing capabilities and lack standard interfaces to connect external sensors. In this paper, we propose MELOS (Mobile Extension for LOw-energy Sensing) a low-cost mobile phone extension that works virtually with all the mobile phones, including low-cost phones since it interfaces with the phone over standard audio port and Bluetooth. The proposed platform augments mobile phones with additional sensing capabilities with minimal overhead in terms of energy consumption. MELOS provides capability to switch on-board modules off as per application requirements while keeping low power interface (audio) "always-on" (to keep the connection) thus resulting in significantly small active mode power consumption. Local storage capability on board ensures that the data is transferred over high bandwidth, high-power consuming Bluetooth interface in burst mode resulting in low energy consumption per byte of data transfer. Interface with a mobile phone ensures that the capabilities of the MELOS platform can be exploited remotely using the cellular connectivity. Using MELOS, we prototype a sample application to monitor energy consumption of several electrical appliances and also demonstrate appliance control using a relay based circuit.