I am working on a project to make tank readers measure the water level for multiple tanks over the farm with no wifi or cell phone reception. I thought that long-range RF transmitter would do the trick but I don't know the best one to choose. It will need a range of about 5 km and will be on land that has lots of hills. It will only be transmitting an int with a length of 6 numbers every 5 minutes.
IMHO the way to go is the Adafruit Feather 32u4. it's cheaper than buying an RFM69HCW, it's barely more than the price of a NANO, and it is both. you need an Arduino at both ends, to program the RF module when you reboot.
search term: RFM69HCW LoRa
if you are a ham radio operator, you can use 433 mHz in the USA. if you are not, you can use the 915 mHz band, in the Feather board above.