Question [Q] On Screen Loupe

Hi, i'm looking for an OnScreenLoupe.
i found a Loupe in the PlayStore but its hard to configure and the app is very buggy.

My idea:
a swipe area shows a rectangle or circle with magnified content by swiping over the screen.
Of course the Zoomlevel and the rectangle/circle size should be adjustable.

Is there already such an app or could someone make it?
(i know there is a similar feature in 4.2.2 but i'm on SGS2 with 4.1.2)