If it's just a single PoE, why not long Ethernet cable from wherever the main Internet connection is? Because you still need the PoE cable, so why not send data over it?
Ubiquity is fun but expensive and in addition to the transmitter you also need a computer (read: RaspberryPi) to run controller on. Mesh generally make only sense when you have a number of these, repeating signal between them, not just a single one.
@kravietz because it is 700 feet away from the router and not an option.
@scully Ah ok, but you do have power in the barn? In such case I'd just go for a directional WiFi antenna (like Yagi) on both ends. No need to top class, 200 m is nothing unusual for WiFi bridges. On both ends you can use TP-Link or OpenWrt WiFi access points, even the cheap ones, you just need one in Access Point mode, the other in WiFi client mode. Chances are it would even worth with directional antenna on the house, but signal may be patchy during fog etc so when you need monitoring most.
@kravietz I have power and a very strong wifi signal. Thanks.
Fantastic place!
I guess Yagi on the barn should do the job, especially if you have strong AP on the house.
@kravietz I plan to repurpose a PoE HikVision camera I already have.