I got an MK802 II to play with the other day, and couldn't help but crack it open. With a little probing I was able to find a serial port, and it happens to have the bootloader and Linux console output. Unfortunately it's a little trickier to solder than on the MK802.
The points to solder are two test points near the edge on the back side (behind the CPU). Ground can be taken anywhere along the border of the board. Tack the wire down somehow as the points are small and might rip from the board easily.

My connector mounting and "case mod":



The 3-pin header is stuck to the top of one of the RAM chips using hot glue shavings and careful application of a heat gun. It's hard to see in the photos, but I had to bend the pins a bit so a connector plug could fit in the cutout.