(2 organizers and a phone) from the 1990s. I'm so nostalgic for this kind of stuff, and the discussion of the UIs and formfactors and so forth was thoughtful if not particularly deep.
The PalmPilot was the first product to combine the form factor, general UI, and organizer functionality we all enjoy on our slab phones today. (Newton was first, but missed the form factor- though come to think of it, large phones are getting back up there in screensize, but the drive for device thinness is even more critical.
(Link via Lost in Mobile, a great blog for gadget and watch lovers. Of course Shaun McGill is an even bigger fan of the Psion than the Palm, and I can't really blame him. His How Did We Get to the iPhone is a nice read in the same area.)