Here is a nice custom KM for monitoring REST API JSON services.
REST API is a very flexible environment without much standard for modeling of data.
Yes its sometimes useful to have monitoring is makes sure a certain service is up and running and specific operations are responding properly and fast enough.
so I created a KM that execute commands for this.
e.g. I want to monitor that TSPS is capable of providing a list of devices it has.
Maybe run requests on social network systems.
the KM allow for frequent renewal of apiKey (aka authToken).
a given service is queries with 1 or more request and each such request is monitored for P&A.
for each one the KM monitor:
status (based on HTTP status)
response time in milliseconds
size of returned response in KB
and a text parameter showing the actual response.
if you want to know more about it, then let me know.
it's basically designed to run on Linux.