This is awesome, going to set this up tonight. I do have one question : what of the 3 pins goes into positive and negative of the relay goes into the motherboard?
The relays aren't here so I can not take a picture but you should connect the cables in NO and COM. If they are front of you this are the left and center one.

I've had computers before that would crash but still respond to ICMP requests. All the popular miners have an API so using an HTTP GET should be more reliable.
Yep, this is in the ToDo list.
Next week I will have a free day and will do the web server first and after that statistics and json-check.