Unfortunately AirClick doesn’t control RealPlayer out of the box, but can be extended with AppleScript.
[Update: I’ve managed to get working AppleScript for adding RealPlayer to the applications supported by AirClick. I will write it up in due time, but in the meantime feel free to comment if you’re interested in an advance copy.]
Download my AirClick for RealPlayer scripts (oops, deleted them in a recent upgrade), including a readme.txt explaining how you might get it working. These scripts work for me, but you use and install them at your own risk.]
[Update 3: Changed title from “Applescripting RealPlayer 10”.]