It's like WiFi. You can have several routers throughout the place, but if you leave those routers, no more Internet for you.
Actually, there's been this theory. What if we could run things like Fiberglass cables under roads, and set up a WiFi network? So we could all have WiFi while on the road? The same concept could be applied to these Wireless thingies, having several stationed at intervals beneath roads, so you always have access to your items.