On the last plane ride, I was watching out of the corner of one eye someone struggling to use a laptop with the seat in front of them fully reclined. At one point they had it open it out all the way so they can see the screen and use the keyboard. But there was no way to keep it in that position because the tray does not have a lip at the right point and the hinge just collapses anyway.
The product the likes of Kensington might make is a portable stand. You crack open the machine, open it up as far as it will go and then pop it on a stand so the thing is at something like a 60° angle. You can't touch type that way, but you can at least see what you are doing. It also means your elbows aren't forced back as far as they will go.
This, of course, won't work on a MacBook Pro - and probably the MacBook too - because the hinge only opens to about 120°.
Given that a brace I guess it's one reason why netbooks or lilliputers have a future: at least you can open them out and see what you are doing when the seat pitch is only 31 or 32 inches.