Auto flush for domestic toilets

First off, I'm not a big fan of auto flush toilets to begin with, but this is for a Customer that is bent on retrofiting. So, is there a reliable and hopefully simple auto flush retrofit for domestic toilets? This is for his elderly Mother with alzheimer's.

Something along this type of product:

http://www.touchfreeconcepts.com/products/auto_flush_toilets.php

toilet

That may be the only product like that at this time.

Then what do folks do?

That have the need. Do they install Sloan? Toto makes a auto type toilet, but the cost is huge. Something like 3K.