Freshping has exactly what I need which is to monitor udp but an enhancement is needed for what I want and maybe you guys will consider this as a suggestion.
In an UDP check you need to specify a command string, but I need to send something that's not really a string. It's a string + some outputs of the PHP "chr" function, which is not really possible to copy and paste into the textbox.
As an alternative I'm monitoring a php webpage which connects to the multiplayer server via ip and via fsockopen, if it's down the webpage returns a 404.
An example: if you have a multiplayer server with ip and port 192.168.10.5:7777 the exact command is
"SAMP" + chr(192) + chr(168) + chr(10) + chr(5) + chr(7777 & 0xFF) + chr(7777 >> 8 & 0xFF) + "i" (a single chosen character)
Would appreciate if this would be possible within freshping.