Just posted in the general iPad thread but this is more apt:|
there's a game out now called Gridlee, which is free, and also happens to have MAME4iOS hidden inside it. Grab it quick before they pull it, especially if you have an iCade! Requires iExplorer to get your ROMs in, but apparently it all works very well.
Pretty much certain Apple will pull it soon though, like they did last time someone hid MAME in an app...
I reserve the right to completely change my mind