Get data from unity app externally

Hello everyone!
SO, here's what I got:
I have a terrain with various POIs scattered in it. I also have entities with limited FOV placed randomly on the terrain. The object of the game is to locate all the POIs by sending the entities in their direction.
Locally, it works great, I used the mouse to click and send.
I wanted to make a network option, allowing to someone else to connect and control the entities. Now here's the catch, I can't guarantee the other person will use unity or even C# and therefor I need a mediator.
Does unity have a REST API like solution? is that even the right direction?