Work is being done on a MAME port for the iPhone. MAME is the Multiple Arcade Machine Emulator that allows you to run old arcade games (provided you have the proper ROM)
![galaga 300](https://images.macrumors.com/t/eovIItMVPszRQSG9_Uqx9aJZzzk=/400x0/article/2007/08/17/galaga_300.png?lossy)
The project appears to remain very much a work-in-progress:
Project to port SDL MAME to the iPhone. The main cool feature I want to add is configurable layouts for touchscreen controls and crazy gesture based inputs. Whether MAME will actually be playable from a performance and control perspective remains to be seen.
Unfortunately, at this time, while it appears to have been built, controls don't work yet.