Android: Call Filter Alarm gives you precise control over which calls push through silent mode and ring, regardless of your phone's settings. It's ideal if you want to get a good night's sleep by setting your phone to silent, while knowing that if a family member or close friend calls with an emergency you'll hear the call.
Before you go to sleep, enable sleep mode in the app. You get all of the alarm clock options you would expect, such as the ability to customise the alarm volume, sound and snooze duration. Then tell Call Filter which people in your contact list should be allowed to get through to you whenever they call. You can also set the app to let allow SMS messages through.
Call Filter can automatically activate or deactivate based on whether there's Wi-Fi present, set repeating alarms, configure alarms with incremental volume, and even give your "always available" contacts specific ring tones or notification sounds.
Hit the link below to grab it, or read more about it at the XDA Developer Forums.