[PRTG] Read RSS Feed

#Requires -Version 4
<#
 ___ ___ _____ ___
| _ \ _ \_   _/ __|
|  _/   / | || (_ |
|_| |_|_\ |_| \___|
RSS Feed Checker
(c) SLinke|Paessler  AG
=======================
Description: This sensor will read RSS feeds configured in
the configuration file and alert as soon as one of them is updated.
The FriendlyName attribute will be used as channel name.
#>
$configurationFile = "C:\Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXEXML\prtg.rsscheck.xml"
$configuration = New-Object System.Xml.XmlDocument
#region configuration
$configuration.Load($configurationFile);
$Feeds               = $configuration.configuration.feeds.ChildNodes
[System.Collections.ArrayList]$Updaters = @();
$MaxMessageLength    = 50;
#endregion

function Check-RSSFeed(){

Write-Host '<?xml version="1.0" encoding="UTF-8"?><prtg>'

    foreach($feed in $Script:Feeds){

        # get the current messages
        [xml]$RSS = (Invoke-WebRequest -UseBasicParsing -Uri $feed.url)
        [string]$currentMessage = $RSS.SelectSingleNode($feed.node).Value
        [string]$oldMessage = $Configuration.SelectSingleNode([string]::Format("/configuration/feeds/feed[@id='{0}']",$feed.id)).saved

        Write-Host "<result><channel>$($Feed.FriendlyName)</channel><unit>count</unit><valuelookup>prtg.rssupdate</valuelookup>"
        if($oldMessage -ne $currentMessage){
           Write-Host "<value>1</value>"
           $Updaters.Add([string]::Format("[{0}] {1}", $Feed.FriendlyName,$currentMessage.Substring(0,$MaxMessageLength))) | Out-Null;

           # save the new message to the configuration file
           $Configuration.SelectSingleNode([string]::Format("/configuration/feeds/feed[@id='{0}']",$feed.id)).current = $currentMessage;
           $Configuration.SelectSingleNode([string]::Format("/configuration/feeds/feed[@id='{0}']",$feed.id)).saved = $currentMessage;
           $Configuration.Save($configurationFile);
        }
        else { write-host "<value>0</value>"; $Updaters.Add([string]::Format("[{0}] {1}", $Feed.FriendlyName,$currentMessage.Substring(0,$MaxMessageLength))) | Out-Null; }

        Write-Host "</result>"
    }
    Write-Host ("<text>{0}</text></prtg>" -f ($Updaters -join ", "))

}
Check-RSSFeed