Floating widget / Overlay on Android launcher
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Does anyone have any idea how this can be implemented?

Some examples:

 - https://play.google.com/store/apps/details?id=gpc.myweb.hinet.net.PopupWeb
 - https://play.google.com/store/apps/details?id=gpc.myweb.hinet.net.PopupVideo
 - https://play.google.com/store/apps/details?id=com.milone.floatwidget

Any idea? Thanks.