I am not sure i fully understand your question But the post below might lead you in the right direction.
In the project there is a VERY simple agent which just make a http post request. This part could be much more sophisticated e.g. the agent could monitor a process which report its status to anvil.
Please feel free to copy the project. If you want the source code for the windows service (agent) i am happy to share it.
But the post below might lead you in the right direction.