Well, it looks like this, duh. (And it's pretty cool.)
Above, you see footage of the Street Fighter IV iPhone port in action, courtesy of GamePro. The iPhone version contains 8 characters, all from the original SF2 cast with the exception of SF4 newcomer Abel: Ryu, Ken, Guile, Blanka, Chun-Li, Dhalsim, and M. Bison (aka Dictator).
The controls are on the screen itself in the form of a button pad and a joystick, and it actually looks like it controls pretty well, all things considered. The video shows a bout between eternal rivals Ryu and Ken, and it's nice to see a great fighting game making the transition to something more portable.
WTB Droid version, please!