The "Download PL2303 Android USB Host API SDK (v1.0.0.6)" bit looks useful...
It is in Java and does not need root access. I wonder if this means they are using the raw device. You might not get actual serial port access here either.
Having to write a device driver in Java is ridiculous... This is what comes with closed platforms...
If you don't get a serial device in /sys/class/tty you aren't going to find a secret hidden serial device anywhere else.
I suspect the number is a meaningless instance number provided by the OS since it increments every time.
well I ordered up a couple of prolifics serial-usb adapters that are supported by there .apk program (they are cheap). see if this gets me started...
updates to come.