Hi diamonddozen - Some members here say it works just fine.

I could never get it to work consistently.  Sometimes it would find my phone, other times it wouldn't. Even when it did, the location was not accurate. For GPS to be efficient, a clear view of the sky is required. A stolen or lost phone will most likely not have that advantage. I gave up on it after arguing back and forth with those ever-so-friendly-and-helpful HTC guys  

But it you want to keep trying, you need to open account and sync both in the app and online - then try the "locate your phone" test while the app is still open. As I said, not very "real world" situation.