Hi I googled shower timer and ended up here. Do you know of any instance where someone has installed a water timer above the showerhead for disabled person with upper body strength issues? Already tried putting a lever on the shower faucet and can't change the whole shower fixture. Seems like pushing a button would be the best solution. Any ideas would be appreciated.

Did your Goggle search take you to the recently posted question here on shower timers?  https://www.askmehelpdesk.com/cgi-bin/yabb/YaBB.cgi?board=plumbing;action=display;num=1087096 830

In that answer Tom suggested adapting a timer meant for lawn sprinkling to a shower.  I think it would mean removing the short, bent pipe usually coming out of the wall and installing the timer ahead of it.  I think the thread next to the shower head is a special thread that may not fit anything except shower heads.  

I didn't think I could add anything, so did not answer that question.  If you need more details on the plumbing, post back and Tom or I will help you.

This sounds like it should work.  More and more technology is available for those needing it.  I am more aware of devices to aid the visually impaired, but learning more about other needs.  

I am heavilly involved with service dogs, and am not sure where to find out about other technology.  

Labman directed you to one of my earlier answers. You may use a mechanical timer or a electronic one. Let me give you a few more sites to check out. www.showermanager.com/?src=K2DG.com/xtnet, and www.showertimer.com.au
If none of those fill the bill click on back and we'll go exploring. Cheers, Tom