I know that a few hospitals have given doctors PDAs in the past. I'm not up-to-date with which are doing so at the moment though. Leicester used to use MedHand Dr Companion software although that is more reference software than patient management.
For making patient lists, I'd recommend HanDBase from
www.ddhsoftware.com as you can pretty much make any kind of database you like with the software including patient lists which can be beamed to each other. You can also encrypt the database to protect the data.