How does it connect to the internet? I don't see eth cable on the picture so I assume it's wifi. In that case you can buy ready made relay modules with builtin ESP32 controller. That would handle the wifi/bt and you only need to write the block checking and opening logic. The whole thing would be lot smaller and would need less power.

Another idea:
Make a subscription service, so apart from the whitelisted users, paid users could access too (I don't know whats inside the fence).