I wrote an application which has the capability of hanging up phone calls when they are received. In order to that I'm using the telephony manager and this permission is required: android.permission.MODIFY_PHONE_STATE
However, this permission makes my app a system app and therefore I won't be able to place it in the play store later. But I've seen apps in the play store that successfully block incoming calls ("Calls Blacklist" for example). I wonder, does anyone know what API these apps are using in order to block an incoming call and also allow these apps in the play store ?
Thanks.