Sounds like an excellent idea. I could absolutely see a market for this. For pricing, I'd build them to be able to work with 'x' amount of machines for 'x' amount of money. Purely examples, but maybe like 0.1 BTC for up to each 5 machines. So if you had up to 5 machines/rigs going you coudl grab that. Then if you had say 8 or 9 rigs, you'd get the 10 machine/rig model for maybe 0.195 BTC and so-on. Obviously you'd have your own pricing based on actual cost of parts and labor, but I definitely think you would find a welcoming market for any kind of remote control/monitoring devices for that matter. Good luck with it though, hope you get it up and going.