How about using a MEMs Gyro based Stylus for combined gesture and touch based inputs for smartphones ?
The stylus would be connected to the cell phone and get its power and data through this connection.
It can have a button which when pressed activates gesture mode and otherwise it defaults to a normal stylus ?
The stylus could be used very effectively for fast data entry and gesture based mode could be used for zoom in / out, forward and back buttons functions on the browser, click and double click ?
It would be built on the lines of the Nintendo Wii remote.