I'm guessing that the streetpass function isn't going to work on my iPod Touch unless I'm in a WiFi area, but this is still really fun.
It has local city, state, country and worldwide rankings.
I got the game soon after it was released, it was funny to see myself ranked at something like 8th in the world, and now after one day my main character (King) is ranked 628th in the world. It stores a different ranking for each character you use, not just overall. My Joe Higashi character only has 2 wins and is ranked 3850th worldwide, so that may be an indication of total users, IDK.
Anyways, its fun and free, try it! Here's the App Store link.
Here's some screenshots:



