Toucharcade has the story:

So, download the game, throw a bunch of ROMs into the ROM folder using an application such as iExplore, start, and you have a fantastic MAME emulator. Expect this to be gone soon. Oh, and it works with iCade!

As developer David Loureiro explains, Gridlee was developed for the Bally/Sente SAC I cartridge-based arcade machine. It has been brought to iOS devices by way of an emulation wrapper…namely MAME4iOS.

When word of this hit our forums, readers were quick to pull out iExplore and begin digging about the app’s directory structure looking for a ROM folder. Well, it’s in there, and sure enough, if one copies other MAME ROMs into that folder, theGridlee app starts up with the standard MAME4iOS ROM listing, allowing for a great many games beyond just Gridlee to be played on the iPhone or iPad in this Universal app.