Via, and as Pixy notes, "it's also a phone."
It has 8MP and 2MP cameras, WiFi a/b/g/n, Bluetooth, GPS, accelerometer, barometer, compass, and a proximity sensor. It can record 1080P video at 30fps. Oh, and there's an FM radio. And a phone.To be a PDA from my SF universe, it also needs a radiation dosimeter, videoconferencing, and digital satellite communications (as the communication system in that universe is satellite-based rather than cell tower based).
"Why a dosimeter?" You ask? Because space travel has the potential to expose you to radiation, more than you'd get on a planet's surface. Ships are shielded so it's normally not a problem, but if you do get a hard dose of something the docs are able to check your PDA and see how much you got and what kind, so they can treat appropriately.
It's also got to pack more computing power into the thing. A handful of Intel Pentium i7 processors would probably be a good start, and a few terabytes of local storage. And better battery technology, as well as a passive photovoltaic panel.
I'm not asking for much...but this is a good start.
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BTW? The screen is a bit shy of 300 pixels per inch. Okay, a typical CRT isn't even 100 PPI, and you have to look very hard to find a printer that prints at 300 DPI these days, but damn does that enable some very fine detail.
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Am I going to buy one? WTF, I'm not made out of money! (And even if I were--"Here, I'll just cut off my little finger and buy this--" Shit, hell no.)
But it's cool.