Beacause I'm having the same problem I want to unlock the safety aswell.
I did a lot of research over here (the Netherlands)
A lot of car-audio shops can unlock the system, for about EUR 100 - 150 (around USD 130 - 190)
it's a software issue which will unblock all video transmit.
BUT!
everytime your merc. will go for a service, the dealer will make sure your car runs on the latetst software, so they do an update. Everytime! Also for your washerfluid level indicator or whatever ... at least, that's the way they do it over here.
Now,
Everytime this is being done, the videosignal is blocked again during driving.
On guy says he does it with a computer and software and attaches it to the COMAND
another guy tels me it's on a readable CD-ROM that just loads into the COMAND and unlock it in that way.
Either way, I would really like to have one of the two, but this is something you have got to have for yourself.
Otherwise every visit at the dealer, wil ruin the fun again.
@ other remark on only drive when driving.
There are other people in my car who aren't driving and want to watch.
it's rediculous to therefor buy these rather expensive screens and installations just that they block the system.
I can't see the use either of watching a DVD only when you are parked somewhere.
BMW has this 'problem' as well