For power wheelchair users who find the joystick controller difficult to use there are various other ways to control and drive a wheelchair. Most of these alternatives are based around switches. Here is an interesting alternative to driving a powered wheelchair which I have recently got on loan.
The TouchDrive 2 is an alternative wheelchair controller from SwitchIt. SwitchIt produce a range of proportional and non-proportional wheelchair controllers. This one uses touchscreen technology to drive a power wheelchair. It can be set-up on power wheelchairs that have P&G R-Net, Q-Logic/ Curtis and Dynamic DX electronics systems, which accounts for many power wheelchairs.
As its due back soon, I made a quick video to demonstrate it.
For more alternative ways to control a power wheelchair, see the following post http://www.atandme.com/?p=950