Sleep Ringer lets you choose only certain people whose incoming call or SMS will RING even if your phone is set to SILENT or VIBRATE. Its functions are fully customizable so that you can pick and choose ringer type and SMS feature. You can use the app either at nighttime while sleeping or during the day at times when you don’t want to be disturbed. Example uses include Doctors on call through the night and business owners that must answer no matter what time it is.