The iPod touch has got to be the last PDA. Smartphones are the realization of the '90s vision of PDAs, with cellular capability and additional features included, but it's interesting how standalone PDAs no longer exist.
Nobody would buy a standalone PDA these days, mainly because they'd need one core feature: Access to e-mail. At that point, you need, at the very least, a WiFi connection, but customers would likely expect a cellular connection.
And at that point, bam, you have a phone.
You could try to make it "not a phone" by removing the speaker and microphone, but people will occasionally want to play a game, so you'll need the speaker, and someone might want to record speech for note-taking, so you'll need the microphone.
TBH, I'm not sure how you could possibly make a "not a phone" PDA.
Nobody would buy an offline PDA. At least, not enough people to pay for the development of it.
Even back in PalmPilot days, internet connectivity was definitely desirable. I suppose Planet Computers' devices are trying to capture some of the PDA spirit by emphasizing the computing, productivity aspects of smartphones with good keyboards.
