The current vision of business apps for mobile devices such as the iPhone are flawed. No one wants to write long documents or presentations on a tiny device. I'm not even sure if people really want to read them there.
The questions shouldn't be "What desktop apps can now work on handhelds?". The real question is "What new types of business apps are now optimal for a device like the iPhone?".
One class of application I think has tremendous but overlooked potential is what I call "mobile command applications". The idea is that what mobile devices are great for is that they allow their owners to receive information and issue concise commands at any time. These simple commands could potentially trigger very complex workflows and actions. A simple analogy is that it only takes a single command of "Fire!" to start a whole war that has been set up ahead of time.
What types of applications would fit this kind of scenario? the requirements are: Time sensitivity, pre-planning (thus somewhat structured workflows), and conciseness of commands.