Jan 25 2011
The accessories that have been deployed in Apple’s proprietary dock connector are highly expensive.
Sensor-Enabled Electronic Boards
Somehow it has been overcome by utilizing the 3.5mm headset jack on the iPhone, like the Square payment system. Recently the University of Michigan’s Project HiJack focuses on generating 7.4mW from a 22 kHz audio tone and the researchers have developedan array of prototype boards for transferring data to and from an iOS app,employing highly economical electronic components.
The boards encompass a functional EKG, humidity,thermal, and motion sensors, for collecting various data. It is anticipated that when the code is introduced by means of an open source license, more devices will deploy the 3.5mm headset jack for the iPhone replacing earphones.
Source: http://www.apple.com