Data from USB drive on Nexus7

I need my application to read a file from a USB disk connected with an OTG cable to a Nexus7.

I know its possible to mount a USB disk on the nexus7 because the app Stickmount does it, but I can't use any 3rd party software for this.

When I plug the device in, I get 2 raw USB device files in /dev/bus/usb/001 (001 and 002) and 2 other files in /dev/usb (bsd1-1:1.0 and scsi_generic1-1:1.)
I have tried mounting these and it didn't work because I guess there is no driver creating a mountable device node.

I don't necessarily need to mount the device (though it would be preferable) I just need to pull the one file off of it (that file will be the only thing on the drive ) so if there is some way to read the raw data off of the drive without mounting, that would be ok too.

Anyone have any suggestions or ideas? Am I going to have to write a driver for this, or has someone already written one I can use?

Thanks