Seeing as how the model A supports OTG mode via the hardware (both the CPU and USB controller were designed for it)
The USB host port inside the Pi is an On-The-Go (OTG) host as the application processor powering the Pi, BCM2835, was originally intended to be used in the mobile market: i.e. as the single USB port on a phone for connection to a PC, or to a single device
I would like to ask how to access and use this functionality
specifically I want to get the Pi to act like a USB flash drive and expose a partition of the SD card via that interface. I intend to use this in my car instead of a USB flash drive, and have the Pi connect to wifi and sync the contents of the drive periodically (such that I do not have to physically remove the flash drive in order to update the content that the car sees). If there are other devices that can do this, I would be interested in them as well (Phones wouldn't work because they need to be turned on via a physical button instead of simply turning on when power is provided).