The two smartphones Hewlett-Packard announced yesterday elicited barely a shrug, and its forthcoming TouchPad tablet is hardly more compelling than the dozens of Android tablets and RIM Playbook tablet on the nearer horizon. So why is HP suddenly considered so upwardly mobile?

In a word, WebOS. In many respects, it was ahead of its time as a mobile operating system, and with the enhancements announced yesterday, it’s that much more compelling on a tablet. The card metaphor works well: Any application, or piece of data, can be a card that appears on the tablet screen, and users swipe through them. It’s mulitasking at its easiest. HP has added the concept of stacked cards, where users can keep related items (Web pages, for example, or e-mails).