- a work phone for sole proprietors or people who work in a small workplace
- a phone that doesn't rely upon enterprise tools like a BlackBerry Enterprise Server or Microsoft Exchange Server and therefore the ability to provision all features on your own
- a focus on the core business functionality of a smartphone, to keep in sync with your desktop or laptop's mail, contacts, calendar, and not games and other consumer functions.
(Photo from Time magazine article, from L to R: iPhone, Motorola/Google Droid, and BlackBerry LINK.)
In this quick and decidedly not exhaustive review--that will be subject to corrections--I'll briefly summarize the four main types of smartphone prevalent in the United States with respect to their ability to deliver core business functionality. But to jump to the conclusion: I'd go for an iPhone on ATT, a Google Android device, specifically the Motorola Droid (or later ones with 2.0 software) if you're on Verizon, OR a BlackBerry, particularly on Verizon, if you need the best voice quality possible and lean towards the "phone" part of smartphone rather than the "smart".