My father is a doctor and I have some expertise in this area (see my blog at). You should look for a PDA that does not have a slideout keyboard, and a minimum number of hard-key buttons. Minimising moving parts like this reduces the number of crevices that can potentially become contaminated with infectious substances, if you’re using the device in the course of your work, and also simplifies cleaning of the device.

I’d recommend a Windows Mobile device, since Palm is rumoured to be currently undergoing corporate transition and software for its OS may be discontinued if PalmOS is not supported in future. Also, most of the medical PDA software out there is supported by the Windows Mobile operating system.

With those considerations, I would normally have recommended a Dell Axim x51v . The Dell x50v and x51v PDAs have the best screen (480×640px gorgeousness!) and processor speed (624 MHz) I’ve yet experienced in a PDA. While they don’t have a massive amount of internal memory, they accept both SD and CompactFlash cards, and that means you could for example, add a 4GB CF card for your medical applications and records, as well as a 4GB SD card for your music - that would be 8GB in total, plus the 128MB on-board storage - a massive amount of memory for a PDA. I believe there are even larger memory cards in both formats available, if you’re willing to put up the dollars.
The only reason I might not fully endorse the x51v is that Dell won’t be making any more PDAs after the x51v; however, it will continue to support its existing models.