*UPDATE*
I found Verizon Fleet Management Tracking Maps and one of the features is "Know at a glance which vehicles are closest to an address, customer or landmark"... Which sound precisely like what I'm looking for. But it's $30/month per vehicle which can quickly add up. I'm sure it's worth the money, but they offer a bunch of features that I wouldn't really utilize at this time. My quest for something similar to this, *but cheaper*, continues!