This is NOT AN APP. It is an addon. Check the description for more info.
This is an addon for the app "Click to chat" https://play.google.com/store/apps/details?id=com.trianguloy.openInWhatsapp
It allows that app to load the list of the recent unknown numbers, by providing the necessary permissions. It will only work with version 2.0 or up.
This app contains the minimum necessary code to provide those permissions. You can't launch it and it won't be shown on your desktop, it will only be useful if you have the main application too (where an extra button will be shown).
I repeat: This app by itself does NOTHING. It is an addon. Installing it without having the main app is totally useless.