@neurrone @adam oh, wow, feeling unsure of having recommended that.
What you mention is called "perfdata" in Nagios terms. Typically, Nagios comes with examples to send perfdata into rrd to create graphs, but I guess that likely won't be good accessibility-wise.
You can provide your perfdata script to send data to whatever works for you (even create tabular text files directly), but that's not likely your best option...
@adam @neurrone may I suggest the classical "sar" utility? It collects performance data on the machine it runs on and it does provide a terminal tabular display. Not sure if it will be great from an accessibility standpoint, but I suspect it's best to try that out first.
(In Debian, this is in the "sysstat" package. I believe you have to enable data collection explicitly.)