When it comes to value-added software on Android phones, I'm typically first in line to call "gimmick!" But today, Sony announced a new service for Xperia phones that actually sounds genuinely useful - my Xperia. It's pretty simple, really. You get a web UI that allows you to track your phone on a map, cause it to emit a sound (it even overrides silent mode), lock it and display a message, or remotely wipe it. And when it comes down to the necessities, those really are the four you need for a "find my phone" solution.
Oh yeah - Google account integration.