Sure, time-based reminders are great, but have you ever wanted to be reminded to do something when you leave work or home? How about needing to remember to do something when you arrive somewhere? "Remind Me Where" allows you to set location-based reminders.
When it runs in the foreground, even with a locked screen, it'll alert you almost immediately. Do you want to switch to a different application and still be alerted? "Remind Me Where" takes advantage of new Windows Phone capabilities to alert you even if you have switched to a different application.
Live tile support. Tile turns red and shows reminder if background alert has been triggered.