Well, it took me awhile but I did get OTG USB Host mode to work on my T-Mobile Galaxy S2, you can now connect USB peripherals such as your USB Flash drive, hard disk (powered independently), USB Mouse, USB Keyboard, and much more. Or you can even charge your other USB devices off your T-Mobile Galaxy S2 in an emergency.
To get it working, simply download the kernel zip file below and flash in ClockworkMod Recovery(CWM) just like a ROM except no wiping needed (just flash).
Download Zedomax T989 Kernel
(USB Mouse working on my T989)