Windows Phone 7 users will have four tools handy to find their lost or stolen devices right from launch and these will come for free for those adopting the platform, via the Windows Phone 7 MyPhone Portal's Find My Phone section. These are: Map it, Ring it, Lock it and display a message and Erase it.
Map it is able to display a Bing Maps representation of the location the Windows Phone 7 device is currently being at. Judging by the size of the circle on the map, besides GPS, the Device is communicating its location using cell tower data triangulation. And while you might be searching for your device within that particular circle, you can use the Portal to Ring your Device with a special
If you fail to recover your Device, you have two more drastic tools of both protecting it and your data. After you create a unique four digit password to assist you in Unlocking should you recover it, you can use the Portal to lock the Device and have a message of your choice displayed on the screen. You have the option to ring your phone at the same time - same as above - so that people hear it ringing. This, together with the message displayed increases the chances of someone noticing a lost phone and even seeing the message displayed.
If everything else fails and you want to protect the information contained on your Device (Contacts, Pictures, Documents, etc.), you can Erase it which will do a Factory reset on your Windows Phone 7. Not quite sure whether that after this step you will be able or not to use the MyPhone Portal for recovering it since it loses its link to the Portal.
While some of these features and services were available before in a one form or the other, these free services undoubtedly increase your chances of finding your lost device. Also, after launch, more services will be ready for Windows Phone 7 users - rumor has it for free.