Best idea I've heard in forever! Imagine them on a beach, dude! It would be so clean because people would get paid to clean it up!

Suggestions:

1. Whatever coin has the lowest fees and highest ability to scale (DPoS ftw) would be best. You're talking about paying in amounts that are usually less than a couple dollars. That'll gum up the blockchain and cost a lot in gas.
2. Maybe even consider putting a basic mining rig in the unit. That way it can be producing crypto to pay out.
3. Power it with solar on top of the unit. Completely autonomous/off grid so it won't cost any money to the owner or the hosting property. Just hook it up to a decent wireless internet connection.

This idea needs to happen man. It would hugely impact the image of crypto being hard on the environment due to energy costs.