Where's my new PDA?

My Palm TX is noticeably wearing out (power button dead and worked around, cover hinge fraying, direction pad starting to go) and doesn't have a decent modern web browser. I might have gotten a Palm Pre by now if it weren't for the lack of full-size external (Bluetooth) keyboard support (notetaking is one of the major use cases) — though I hear there might be an SDK coming out which would let third parties build one. (Lesser issues are the cost of a phone contract (though Internet-anywhere makes that have a good bit of value) and the battery life.) I get the impression that I should be looking at the Nokia N900 or one of its relatives, but I haven't gotten around to investigating that.

My additional requirements for a New PDA are that it sync calendars/todos with iCal, sync the abovementioned notes to my Mac (I don't care what software), fit in my shirt pocket, and have mostly-not-locked-down-and-expensive software development/installation (so that customized/open-source/the-obscure-niche-I-happen-to-need software can happen).

(Apple mobile products fail on the openness criterion and either Bluetooth keyboard (iPhone/iPod touch) or fitting in the shirt pocket (iPad).)