I haven't seen anybody roll up to their desk reach across and touch screen. Far too much ergonomic fatigue.

Touching screens brings with it the grease, oils, buggers, snot, and fecal matter on fingers. Cleaning a tablet is easy because it's small &  mobile.

I screwed a 1x8" board & brace to the arm of my desk chair painted them chocolate to match the chair. Then added a piece of tool box matt and put one of these on top. http://www.logitech.com/en-us/product/wireless-trackball-m570 The mouse is made for big hands, off the desk and always where it belongs plus nearly zero fatigue - no reaching.  

Matched it to a backlit wireless keyboard. These are paired to a couple of laptops so a quick off-on allows use with the laptop