I've done quite a lot of work on an aerodynamic experiment rig recently and found that cheap food ties (the sort you get for doing up sandwich bags) work great for keeping cables together and are a lot cheaper and less permanent than cable ties; sure they're not great for heavy loads, but most of the time they keep things neat. Also learn to coil cables properly: http://www.youtube.com/watch?v=lLwwB29uQRg; you're not always going to have cables that are properly cut to length and using this method allows you to coil cables in the centre of the cable if necessary without causing extra twisting or tangles in the cables.
There are several ways that existing codes could be used but the chances are that two random people will not both know a code that could be used. Of course if one knows one say morse then they could write the alphabet in morse and hope the other person understands that it is the alphabet. I would be interested to see exactly how these screens work, they would have to move fairly fast to be impossible to write on. I'm tempted to create a game like this just to test out with my friends.