I'm looking to get information on whether or not I'm active on my computer. Particularly, I'd like to be able to query whether or not the computer is on, off, or inactive (on but no keyboard/mouse movement). This is not the computer that is running node-red.
You could use the ping node to determine whether it is on our not, assuming it is accessible from the node red machine. To tell whether it is active or not is much more difficult, you would need to have some s/w running on that machine I suspect. I suggest running node red on that machine too.
I wouldn't mind an extra piece of software on that machine. I tried looking for one but couldn't find what I was looking for, suggestions are welcomed on that front.
That will rather depend on what operating system you are running.
SNMP not for the faint hearted? I struggled with MIBs (especially the custom ones) until Nagios (CORE) came to rescue for my farm in another way. Unfortunately, I cannot plug its dashboard to the preferred Node-RED dashboard.
I'm using Windows.
WMI is what you need to look at - Windows Management Instrumentation. If there is data to be had, you can get it through the WMI APIs.