HiJack is a hardware/software platform for creating cubic-inch sensor peripherals for the mobile phone. HiJack devices harvest power and use bandwidth from the mobile phone's headset interface. Several energy harvesting power supply designs are possible, with tradeoffs in efficiency, cost, and complexity. Digital communications of sensor data across the audio channel offers several coding and compression opportunities. The HiJack platform enables a new class of small and cheap phone-centric sensor peripherals that support plug-and-play operation. HiJack has been tested with the iPhone 3G/3GS/4G, iPod Touch, and iPad devices. We're working on supporting Android and Windows Phone 7 devices as well. The HiJack platform has served as the basis for a number of low-power sensor and signal conditioning front-ends including EKG (both 3-lead and two hand), gas concentration (CO, NOx, O3, and SO2), and soil moisture. More project information can be found out on the following link: http://www.eecs.umich.edu/~prabal/projects/hijack/.
The main tree for the HiJack system can be found here: http://code.google.com/p/hijack-main/, a refactored version of HiJack for Android can be found here: https://github.com/ab500/hijack-infinity, and a HiJack oscilloscope can be found here: http://itunes.apple.com/tw/app/id434388871.