The DJHI 2.8 is now available for preorder. The DHJI acts as an alternative serial connection in order to protect the Didj from the 12V signals it would be exposed to with a direct serial connection to your PC. It also adds in a microSD card slot and makes the connection process as simple as plugging it into the cartridge slot.
[The Moogle], who was the winner of our second Barcode Challenge, also tipped us off about his hack that upgrades the Didj to 64 Mb of RAM.