Is there a Gmod app for the iPod Touch?

Answer 1

No. and there never will be. Garrysmod (i think that is what you mean) requires a fast processor and a fast graphics card. it exceeds the capability of an iPod touch however i don't doubt that there will soon be portable phones capable of playing games like this

Answer 2

unfortunately there is not, this is because garrysmod is a big game and wont be able to have every add on installed onto it, even if Garry does choose a few ad dons which are only going to be allowed on garrymod, it will take a lot of memory even for xbox or ps3.