The Sleep Guard application is a simple and convenient call and SMS filter. In fact, it's a white list. Sleep Guard will allow you to filter incoming calls and SMS from all contacts except those that have been added to the list. When you receive such a call or a message, the app will automatically disable sound, and when you receive a call or a message from one of the contacts of the list the app will enable it. It also allows to terminate incoming calls (not only to disable sound).
The Sleep Guard application will protect you from those, who likes to call early in the morning or late at night, and at the same time, you will never miss an important call!