IME Plan B is the best app for this, but I haven't tried all of those mentioned. You use Plan B after losing the phone. You go to the market on your PC or another Android device, and remotely install Plan B on your phone, which will then turn on the GPS and start sending text messages with the coordinates of the phone, which can be used to display the location in Google Maps. It will use the network location if necessary, and it may be, because the GPS may not work where the phone is. Being inside a large metal building can result in no GPS signal. You may be charged for a lot of text messages, but that's a small price to pay for finding the phone. I tried it just to see how it worked, and it showed my phone in the correct room in my house.