You could try Zigbee. It has range up to 10km. It also appears to run in the licence-free band in many countries.

https://electronics.stackexchange.com/questions/106171/xbee-and-zigbee-for-long-distance-signal-transmission

https://ham.stackexchange.com/questions/3729/do-you-need-a-radio-licence-to-use-zigbee-xbee