Well the Palm Pilot isn't multitouch so ofcourse you can't do a pinch there. But double click just works out of the box on almost all devices when an existing OS is used.

I think you should give this a read: http://www.billbuxton.com/multitouchOverview.html and notice these words: "What I am pointing out, however, is that "new" technologies - like multi-touch - do not grow out of a vacuum."