QuiteSleep is an application for Android 2.0+ that manages your incoming calls when you're busy, sleeping, or doing anything between two time slots in any day of the week. The app can mute a list of callers and send an SMS or e-mail with a predefined text to let your callers know you're busy, sleeping, etc. This is an open source app distributed under the GPL v2 (or later). It uses db4o for persistence and it's available on the Android Market.