How make an Overlay who only detect gesture. Android 4.x

I try to make a service who put an invisible overlay (transparent layout) on top of everything and detect the gesture for bind an event.
but when the overlay is on top, everything under is inaccessible (Applications).
I have use this example : url (bejause i can't post a link ) : awsware.mobi/code_OverlayView

How to create an overlay to catch gesture without trouble the others applications.