I agree with cevu.
To add the external DVD, you would be utilising the reverse camera screen. (ie. hijacking the reverse camera mod).
If you were already doing this mod, you better off doing sat nav hack instead.
As for this hack, yeah, see ya later warranty! I assume all are familiar with the procedure. Quite straight forward but at the moment, guys are cutting and splicing into the wiring looms.
Having looked at the pin outs and what is actually being done, I do think it is quite safe, IF DONE CORRECTLY, but obviously, if there is an un-related failure with the unit, you don`t have a leg to stand on come warranty if wires are cut.
(I DO STRONGLY SUGGEST IF YOU DO HAVE ANY CONCERNS, DO NOT EVEN THINK ABOUT IT!!!)
I will be toying around with mine in the coming months and hopefully I will come up with a procedure that won`t involve cutting, but rather removing pins from the plug and utilising jumpers that are easily removed in the event that the un-speakable should happen!
I will keep you all posted when I eventually do it.