The patent is not really about double-click but about a way to use a limited input device (i.e. a cheap button on a mobile phone) to trigger more than one function, morse code sent from user to the mobile OS if you will. It adds functionality without increasing cost nor adding clutter. What it does is map functions to like this:
Down-Up -> F1
Down-1/2sec-Up -> F2
Down-1sec-Up -> F3
Down-Up-Down-Up -> F4
and so on.
IMHO, this is not a trivial patent but a rather innovative new use of existing technology to overcome limitations of mobile devices. Is it a general innovation? No. But it is innovative if you consider the context of its application and you would not think it is an obvious solution if you were the one assigned to solve this problem.
Frankly, I prefer my Next-App (aka Appy) button idea better since user doesn't have to remember the correct pattern. Instead, the user just flips apps as if flipping pages until they get to the one they want to use. In the end, users remember 'where' the app is (i.e. 3rd app) and click the button that many times as they move the device up for use.