Using a website, the Sony Xperia owner can arrange for his missing phone to sound an alarm, even if the phone is on silent. Other options allow the owner of the phone to lock down the device, or just in case there is information on it that can threaten the free world, wipe all data off the phone.
For 'my Xperia' to work, the phone has to be on and have a working connection. The Locate feature will show you on a map where your wayward Xperia is. If the device cannot be found, an email is sent to your Google account once the device is located by the service. You can also arrange to have the phone locked using a 4 PIN code (don't use S-O-N-Y) and it replaces any existing screen locks on your phone. One of the best features allows you to write a message that will pop up on the screen. Something like "This is the police and we have your place surrounded," might come off sounding lame. Do put your phone number at home on the message just in case your phone was found by a honest person.
source: myXperia via AndroidCentral