Q: When I turn my ringer off to sleep, can I set it so important contacts can ring through anyway?

I'm not yet an iPhone user. I saw a commercial that led me to believe that I can set the iPhone 5 so that specifically selected contacts can ring through, even if the ringer is turned off while I sleep (think Mom, Sister, friend stationed in Afghanistan). That was a deal breaker for me at my last upgrade, but if that option is available, I will definitely choose an iPhone for my current upgrade.