I was giving more thought to the action bar on a smartphone, and I'd have to retract my assertion that it wouldn't be practical on a smartphone. Why? Because I use an N810. Let me explain.

In honeycomb, the action-bar is implemented as a fragment along the top of the screen, that displays context-appropriate options. It take up real-estate, and since it contains buttons, it currently takes up slightly more real-estate than the current statusbar on smartphones.

However, on my N810 with its 800x480 display, when not in full-screen, displays a top bar as well, with a main menu and 'status bar' icons along the top. Based on what I've seen from Honeycomb apps, there's no reason something similar couldn't be implemented on the smartphone in landscape or portrait.

In fact, the N810 displays not only a top bar, but often a bottom bar and side bar when not in fullscreen. What's left is a smaller window, however, it illustrates that it is possible to have these bars without hugely sacrificing functionality.

In my opinion, one 'action bar' would be enough, and I would prefer not to have multiple bars as not to take up too much of the screen. But a comfortable implementation would have to be discovered.

Needless to say, I'm interested in what Google comes up with!