The best Android phone locator apps are SeekDroid, Where's My Droid, The Lookout Mobile Security and Prey Phone Tracker. These apps have features like siren activation to find a nearby located phone and settings that are managed through a secure website. You can get these apps at bestandroidappsfor.com.
As of 2013 the best phone locator apps are PhoneLocator Pro by developer RVO, Where's my Droid and Seek Droid in that order. Phone locator apps need to do more than just locate your phone because what if your phone was actually stolen. Wouldn't it be nice to take a picture of the thief that has your phone for your local authorities in addition to tracking the phone? Seek Droid can't take pictures of the thief that has your phone so it ranks last on my list. I'm speaking from personal experience because I own all three of these apps. I'd even suggest looking at the app GotYa before I'd consider Seek Droid. Seek Droid would be be good as a family locator type app because you can set boundaries that will trigger alerts if a phone is taken outside preset boundaries e.g. tracking your kids.