Obviousness
"The problem is patent authorities are reluctant to invalidate patents on the grounds of obviousness. It is generally taken as a weak argument. This is because many good inventions appear obvious after the event. A good example is the Black and Decker workmate, which essentially combined a work-top with a clamp. The guy who came up with the invention spent quite some time and effort trialling it."
The workmate example is often cited, but workbenches and clamps have been around for thousands of years. If no example of a workmate could be found - give the man his patent.
The problem with the sort of patent at issue is that new technologies are entering the market all the time and a whole legal industry to devoted to filing patents that imagines uses for these. In reality, 99.99% of the worthwhile ideas are truly obvious - multiple development teams would independently think of the same idea. These patents then become anti-competitive corporate weapons, rather than protecting true innovators.
In my opinion the burden of proof should be on the defense. The fact that someone thought of a feature before handheld displays were common should be a strong point against it. Someone unware of the patent, independently having the same idea should also score against it. For instance, I would bet that the Apple team who introduced the feature tried to patent it and ran up against the BT patent - which they then brought.