Connecting a few dots here and it looks near-certain that the S3 will support WiiMotes on stock firmwares over bluetooth, and PS3 controllers via USB OTG, and also have support for midi devices via USB OTG. Pretty cool stuff. Details.
I did a ton of research into USB On the Go (OTG) today, totally separate of your post. It's very very cool, if your phone supports it. Allows you to plug USB devices of any type into your phone - if your phone has drivers for them, it can use them. My phone does OTG (thankfully) but it has power issues and needs a bit of a contorted setup with a y cable and usb hub (other phones just need a OTG cable available from amazon cheap).
Also, my phone works with the wiimote - that's very cool, and they're so common, works well ... (have I used it with FPSE or just snes emus?)
Anyway, thanks for the heads up.