I've never really figured out how to do work with anything less than a full computer. I've tried everything: Palm Pilots and Pocket PCs in the early 2000s, laptops, and eventually I just settled on just dragging a (smaller) laptop almost everywhere circa 2005. I get the feeling that, most people who have been thinking about mobile technology and productivity assume that the only impediments to mobile productivity are better hardware and software. Contemporary (multi)touch screen devices are the current embodiment of this theory.
I'm convinced that the theory is wrong.
Having better and more powerful technology doesn't hurt anything. I'm a huge fan of the smaller, integrated, and more powerful devices. Software written specifically with mobile users in mind does improve the potential for productivity. These technological improvements, however, make the underlying problem more apparent.
The challenge of getting things done when mobile has little to do with the capabilities of the mobile platform, and more with the way people think about and plan work when mobile. Not only is this hugely frustrating to users, but technological capability that people can't use threatens the ongoing development and adoption of new technology.
Using Mobile Technology More Effectively
The solution, here, I think is two-fold:
Fully Integrated Applications
Let's develop integrated applications, not just integrated devices with different applications. Just as we didn't need separate devices for every mobile function: telephony, music playing, book reading, mobile internet, and so forth. We don't need different applications for every function: calendaring, messaging, email, contact management, notes, reading, and so forth.
At the very least applications need to be highly interoperable, so that users can send data between application functions easily, and synchronize data back to desktop and web portals seamlessly.
Task Planning Strategies for Mobile Productivity
I don't think that the "user stories" for mobile technology are really fully developed, and as a result any interaction with a mobile device that isn't responsive (i.e. there's an alert of a new event, and people respond to it,) is either "twiddling nobs" (i.e. non productive,) or entertainment focused (i.e. playing music, video, or opening a book.) Perhaps that's enough for some uses, but these this kind of workflow covers a small percentage of what people do with computers.
If mobile technology is going to replace a general purpose laptop, ever, even in limited situations, we need to figure out how to work in different ways. I know that I am loosing a great deal of time, when I'm using my phone switching between the notes app, the reader, the task list, and the calender. This task switching gets in the way of doing things to a much larger extent than similar behavior does when using a conventional computer. I would even posit that, the cost of context switching is inversely related to the size of the interface.
Better application integration will help this, but I think the real solution is providing a method for people to organize their mobile time more effectively. The task list that we build for ourselves when we're doing "conventional" work (i.e. things that we need to remember to do, open projects, open issues,) aren't particularly useful or usable when we're looking at a tablet or a phone. If we don't know what we ought to be doing, it doesn't matter what the device or software is capable of in theory.
There are probably a dozen or more solutions to this problem, but here's my first stab at it. What if there was a way to "forward tasks" to ourselves when we're on the run, but have a few moments? We all loose time waiting in queues, or waiting for trains, and these seem like ideal phone times. If we had a way to queue things for ourselves, so we could spend the time doing something. Even better, would be software that would not only collect and display the queue but would also connect with the application where whatever needed to be done was and then record the results and send the back to our desktops when we were done.