Not sure if this is new or not but Winegard offers Dish Network, pay as you go for RV's. You can purchase up to 3 - 211k HD receivers and either add them to your home account for $7.00/mo each or buy 30 days at a time for full access including distant networks (website says distant networks to follow).
This receiver apparently adds off air stations like Waynem was discussing in another thread. You can also add an external hard disk for the DVR function and move it between the house and RV.
I called Dish and they said that they don't do this direct and that you have to go through a retailer such as Winegard. Winegard activates the receiver(s) and just adds it to your existing account or can setup an account.
I thought this option might be better for us. I ordered a receiver today (159.00). We'll see how well this works.
Further info:
http://www.winegard.com/dishnetwork/
Ken