well, the usual way to do that is reading loadavg with a timer.
Total CPU load is the first value and should be multiplied by 100 to get the percentage.
But you can also read that into a memo, label, whatever, in code.
Note that "everything in Unix is a file" applies here: It is a real time value. You can connect it to a timer.
E.g. the TOP command/program also utilizes loadavg.
program cpuload;
uses cthreads, classes;
var
s:Tstrings;
begin
s:= TStringlist.Create;
s.loadfromfile('/proc/loadavg');
writeln(s.text);
// etc;
s.free;
end.
Untested, but should be close.