Call Blocker let's you mute all callers except your selected group or contact.
Activate Call Blocker by touching the phone-image in the application or the widget. When the image is crossed over the blocking is active.
Call Blocker mutes the sound of the phone unless the selected group/contact is calling you. This means that if you explicitly turn the sound up, you might hear a few rings before it is muted again. If your phone is muted by default Call Blocker will not work. When someone calls you the screen will be unlocked as usual.
Rooted devices might have to explicitly allow reading of PHONE_STATE for Call Blocker to work.
This application was created for my girlfriend who work a night-shift and need help from friends to get her out of bed at the right time.
Italian translation, thanks to Veronica!