You would probably need to install a script on the target PC which sends the values to your server - eg, inserts into a database.
ie...
1. Shell Script:
Collects the information.
Goes to a URL (eg script.php?ip=192.168.2.2&power=240W) (you could have it launch this URL in a browser window or there is probably a command line way to do this too).
(You could do this with PHP but you would need a local version of PHP on the machine and you would still need exec() I think).
2. Server PHP: script.php
-
$ip=$_GET['ip'];
-
$power=$_GET['power'];
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$query= "INSERT INTO power SET ip='$ip', power='$power'";
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//run query
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3. Schedule
Have the shell script run at regular intervals on the target PC.