Dear Verizon, AT&T, Sprint, and T-Mobile:

You’re losing out on a big opportunity.

There is a product that you could introduce with off-the-shelf hardware that would fly off the shelves if you priced it properly. Some of you already offer something very close to this product, but you treat it as a red-headed stepchild and hobble it.

There are now hundreds of thousands of iPad owners who have the WiFi-only model and are discovering that there are places they wish they had connectivity. You could be capitalizing on this buyer’s remorse.

If you offered a small 3G-to-WiFi router that was designed to be mounted in a car, and bundled it with service plans that approximated Apple’s deal with AT&T—no contract, limited or unlimited, come and go at will, and pricing in the $20-$40/month range—you could pick up a lot of customers.

By making the device designed to operate in a car, you’d limit it to mobile use. It’d be more difficult to use it instead of a broadband connection in the home. That’d inherently limit any perceived “abuse” of your networks.

You’d have to price it to compete with the 3G iPad. Yes, it’s not as lucrative as the gold-plated Cadillac data plans you’re offering with similar products today… but really, how well are those things selling outside of the dedicated road-warrior outside salesman market? Think big: a little money from a lot of people.

Heck, you could even design the unit so it only operates on the 5GHz 802.11n frequencies. That would keep it from penetrating walls efficiently and effectively tie it to the iPad; Apple’s practically the only company that offers 5GHz functionality across its line. Then you could still sell the rip-off routers to people that want 2.4GHz. Plus, then the device wouldn’t be competing for the scarce spectrum allocated to 2.4GHz WiFi.

So how about it? The world might not beat a path to your door, but I know I would, and I bet a good percentage of the half-million or so other iPad early adopters would as well. It would be an effective way to work around AT&T’s U.S. monopoly on 3G iPad connectivity.