Adding water for icemaker.
 

Lowes and a fantastic PEX kit that you can splice into the drain lines in your coach battery box. It comes with a on/off valve and took all of 5 minutes to install and run across underneath and back up through the old LP line hole. The only down side is you need a cutter but I had one. In the winter when you drain the lines the icemaker line will drain automatically.

i guess you 1st have to have a fridge capable of having (or adding) an ice maker....to my knowledge if your unit didnt have the option they can not be retro-fitted (unlike most residential fridges).