Activities and customization in mobile UIs

This paper provides an activity (not activity theory) based approach for structuring UI (user interface) designs for mobile computers. They also explore the concepts of zooming (an underused navigation method IMHO) and user-customization. The author views activities as being higher level processes which people complete through individual tasks. I'm not sure why the idea of tasks and sub-tasks wasn't sufficient, but here's a new term for it. The paper also advocates increasing the level of customizability to the point where users can practically create their own applications for specific tasks.

The two common arguments about customization:
for:
it increases user freedom and flexibility, while reducing the need for the designer to predict user needs
against:
it complicates the interface, reduces consistency, and places unnecessary cognitive load on the user

The answer is likely somewhere in the middle, but this paper is on the extreme end of "for". Given the fact that mobile users rapidly become experts at some functions given the heavy usage of the devices, they may have a point.

Activity-Based Mobile Interfaces, 2001
Towards a user model for Hybrids between Mobile Phones and PDAs
Staffan Björk
[Full-text pdf]