Droid inPocket Free

Set it and forget it: your phone will get smarter for free.

There is now a Premium version that offers text to speech for sms messages and contact names: https://play.google.com/store/apps/details?id=org.addition.inpocket.premium

Auto-adjust your ringer/vibration.

inPocket will set your phone to vibration mode when the phone enters your pocket or when it is facing down.

When out-of-pocket, ringer volume will adjust automatically to ambient noise level: if it's quiet volume will be minimum and when on a loud place, the subway for example, it will try to be audible.