I loved this feature on my BB and really missed it on the S2, along with a notification led. But, I found an app that works great. It's "Who Is It". You can get it in the market. It's not free, but I couldn't live without it. When I silence my phone, it still allows calls from all my family members and close friends to come through. I needed it because I wanted to make sure they could all reach me in an emergency. I also assigned different ringtones to each one so that when they do call, I know who it is by the tone. The email ringtone alert doesn't work anymore since Google blocked third party apps from access, but I can live with that. You can try it free to see if it works for you.