I don't know if there is or not - seeing that I don't have an iPod at the moment.
You should probably search for it while on your iPod and if you can't find it then they don't have one.
But yes, I do think there should be one. It would bring more convenient for people that can't be on their computer all the time when they want to be on AG.
I will tell you, though, that I'm able to get on AG with my PSP, so I think that you might be able to without an APP.
If you have a search engine then you can look up Armorgames, I have a Itouch and I have the whole website on it. The only thing you can't get is the games. I only use it to go on the forums when I'm away from the computer.