BlackBerry Shield is a new service from RIM that will be out around April of 2010, BlackBerry Leaks reports that the details of Shield have oozed out to the Internet. We know that the service will include remote device wipe, which will allow you to log in from a computer and pull all the data from your phone/memory card.
There will be a "lost and found" screen that allows you to display a custom message on your phone if it is lost. There will be a remote password set/reset ability, and a loud bell alarm that you can set off remotely with Shield. You'll be able to turn GPS/GSM tracking on remotely (which is actually a little scary) in order to see just where you left your damn smartphone.
The cap in Shield will be a wireless backup and restore service. You'll even be able to program your phone to automatically back-up every so often. In essence, Shield will turn the loss of a smartphone from a horrifying disaster, to a minor inconvenience.