Many of us keep our mobile phones on silent or vibrate when we're out and about, but this can let important calls slip through your fingers. Reader nikils015 shows us how to let calls from a few choice numbers alert you loudly.
I work the third shift, and have missed many important calls during the day when my phone volume was off or on vibrate so I could sleep. Finally, I thought to give certain trusted people the password I had set to my phone's Where's My Droid app. Voila! In an emergency, if a certain word or phrase is texted to my phone, the ringer turns itself on and rings to wake me up, and I can always be reached.
This is a really good idea. It's common courtesy to not let your phone blare its ringtone in public places (especially in certain places like the office, or funerals), but it's nice to have this backup in case a close friend or family member needs to notify you for an emergency. Note that if you already have an app like Tasker installed, you can build a very similar profile based off a received SMS.