Good references to this area can be found at The Legion Project and The Globus Project . Ubiquitous Computing Tools. While such mobility, portability and ubiquity will depend heavily on authentication and directory services, additional protocols and APIs need to be established. For example, standard sets of data will need to be moved frequently and securely between devices and centralized directories. Mechanisms are also needed to change attribute preferences depending on the characteristics of the device being used.
References are harder to find.
One is Project Minotaur .