MapPoint : Using Geofences in MapPoint Location Server Applications

I just came across a cool article that explains how you can achieve many tasks using geofencing that seem un-doable otherwise.but what the heck is geofence ? yeah .. read on according to the article ..

A geofence is a geographical region that you define and use to trigger an event when a user enters the region. For example, you can create an application that sends an Short Message Service (SMS) message about a current sales promotion to provisioned users when they come within a one-mile radius of your store location.

so what do you think ? where can you use it ..? to check whether your kid is actually in the school ? to spy on your spouse ;) ? to monitor all the prisoners in a prison? its just limited my your imagination .. so think !!