You can explain more what json-rpc.txt is and how to see miner stats in json format?
I have to write some more documentation when there is time for it ofc

For more description just start zm without parameters and you'll get help on the new telemetry option.
So if you start zm like this: zm ...... --telemetry=0.0.0.0:2222
Just send to the host zm is running on:
{"id":1, "method":"getstat"}
and you'll get a response:
{"id":1,"result":[{"gpu_id":0,"temperature":0,"sol_ps":0.00,"sol_pw":0.00,"avg_power_usage":0}],"error": null}
You can try it with netcat:
echo "{\"id\":1, \"method\":\"getstat\"}\n" |nc 127.0.0.1 2222