Q: Disability accessibility (mouthstick) and touch screens

As long as the tip that touches the screen is of the right material, it should work as well as you could expect.  I googled, and found at least one available

http://www.etsy.com/listing/64832134/ipad-mouthstick-stylus

It is a different type of screen.  Not touch sensitive, but capacitive sentive, so whatever you touch it with need to have electrical characteristics similar to your finger.  

Actually, a stylus sock sound like you could turn almost anything into a 'toucher'. 

A company called iFaraday makes mouthsticks designed specifically for capacitive touchscreens (such as the one on the iPad, iPhone). The company provides a variety of lengths, from 9" to 18", all for $20. Also, they are willing to work with you to make a custom one if what they current offer don't meet your needs. Might be what you're looking for!

http://ifaraday.com/MouthSticks.html

Hi there!

There are better ways to use an iPad now if you are unable to access the touch screen. In iOS7, Apple incorporated Switch Control that allows you to access and control the iPad with a variety of assistive devices. This one, Tecla Shield, allows you to use any switch or the driving controls of the weelchair to control the iPad. Check it out:

http://gettecla.com/pages/tecla

Hope this helps!