I figure since HDMI is already listed as one of the features supported by the device, it would work better to go ahead and work on improving the device by making sure that HDMI Consumer Electronics Control ( CEC ) is added. This should work out fine since it's only connecting one pin on the HDMI port. As for the use of HDMI CEC it's a in-wire control system used to control devices like dvd/bluray players, televisions, cable set top boxes, sorround sound systems, and numerous other devices. There is already open source work on this using the Arduinoboard ( atmega series chip ) and the TI msp430 chip.
As for the hardware changes, this involves Pin 13 and 17 of the hdmi cable.
As for the library status, Currently a GPL v3 library exists for the TI MSP430 chip, and it can probably be modified to work on the allwinner chip.
Google Code: cec-arduino - Arduino library for communicating with HDMI CEC equipment
FreeDesktop.org - CEC repository- TI msp430 linux changes and CEC library
Wikipedia: HDMI - Details on the hdmi specification.
This would also make the chip ideal for use with XBMC for Home Theatre purposes. Currently an external dongle is required since very few GPUs support this natively see XBMC and HDMI-CEC