In Europe, rescue insurance is common for mountaineers. Probably what would be a good idea is to have a rescue insurance program that is part of the purchase of a SPOT or PLB. In other words, you pay an extra $20 or so when you buy it, and that signs you up for the insurance. Since the vast majority of units will likely never be used for an emergency, you have lots of people paying $20 each and just a few actually being rescued.
SPOT actually has a rescue insurance program available on their site as an option - $7.95 per year. Just make that a part of the deal instead of an option, and there you are. Especially simple with SPOT, since you have to have an annual subscription anyway.