The simplified version of my current project is I want 2 Arduinos to communicate over 50km+. I will have a phone within a few feet of each arduino which means possibly Bluetooth or phone data is an option. I was thinking perhaps something even wilder like email or sms could be explored. Or perhaps I need to create a phone app that the arduinos communicate through, not sure.
The longer version of what I am trying to accomplish is the following.
If User A clicks button A attached to Arduino A then an LED that is attached to Arduino B turns on. This works both ways too. So if User B clicks button B that is attached to Arduino B then an LED that is attached to Arduino A turns on.