Handheld Learning - learning with mobile and ubiquitous technologies

Devices that don't seem to have been mentioned much are the A5 displays in common use in a lot of commercial and public sector environments.  Parcels delivery, building maintenance, fire engines, police cars, building inspection....

LOTS of A5 screens, some in car, some dockable.  Work over GSM, GPRS, Mobitex ( as was) and now, with the new mmO2 tablet over TETRA as well.

Anyone done any learning on these?
Any pointers ( because I'm trying to get some interest in this for a project)?

For manufacturers have a look at Futronics, Cleartone, Microbus, Symbol, mmO2.......