ID Cards (Part 3)
It's been pointed out to me that the obvious device to hold user controlled personal information is the PDA enabled cellphone, not a pure PDA. On current trends, by 2010 full-featured cellphones will be owned by over 80% of the population. So the marginal cost of supplying them to the remainder will be modest.
This approach has the added virtue of providing a universal "999 + location" capability to every citizen, (by then the ability to provide location will be ubiquitous). If the Brit police got their Rapid Response act together, this would make a serious dent in the very high UK personal assault rate.