I am contemplating how to adopt a web site to be more suitable for the mobile phones. I have stepped on a set of solutions that may provide an answer to this question and cover more than one phone type.
Writing application for each phone seems a bit tedious business. I guess that producers will hit the wall of cross compatibility. It is cool to have a native app for your phone, but multi-phone development is costly, and maintenance of several lines of mutually exclusive phone os-es applications even more. Thus I guess we will go to a deadend with specific apps (except for games and system utilities for each phone). Already top 10 apps on iPhone are games - I've seen nothing serious.