How to do android assistive touch like iphone or EasyTouch app?

Question

Title pretty much says it all. I want to have the assistive floating button that stays on top of all other apps (even in games). A good example is EasyTouch in the Play Store. When clicking on the floating button, I want to open a floating layout just like EasyTouch. EasyTouch doesn't require root. I search everywhere but could not find the solution, so any pointer would be appreciated.

Thanks a lot!

Edit: Easy Touch can be found here https://play.google.com/store/apps/details?id=com.shere.assistivetouch

Solution

There are a couple of APIs in Android that can create system level views. See this question. It seems to me that assistive touch-like app can be built on top of it, though I did not try it out myself.