Capcom Arcade is almost like a modern-day shareware application for the iPod Touch and iPhone, that allows you to play Street Fighter II, the original Ghouls ‘n Ghosts, Commando and 1942 for "free" on your iOS device.
Each day, you’re given three free plays for three single games. Once you use up your free play "continues," you can either wait for a free renewal the next day or buy more play tokens. You can buy ten tokens for $0.99 or just buy an "unlimited play cabinet" for $2.99.
You can grab Capcom Arcade at the iTunes App Store.