GPS-tracker-based delivery service

Most delivery services rely on addresses, but this isn't helpful for people on the move. It would be helpful to be able to order something and have it delivered to your GPS coordinates at the time of delivery. The service would need parameters (e.g. remaining in the same city), and would need a feed from your GPS or other location device (e.g. cell phone triangulation).

Potential uses: ordering takeout that is delivered to you on your walk home.