@ksiva - Ack.. So basically, the user's device has to be absolutely stationary (not held in quivering hands). I think the complication with movement from the camera + targetobject in the posemode set to target might have been causing the weirdness.
Right now, I'm just trying to create simple toy projects to test out some ideas -- say, using the marker/imagetarget as a paddle for a virtual ball (paddleball, AR -- with or without the string tied up).
It's easy to get that to work for Unity Desktop, as there's even a built-in bounce physics material, but the same thing looks like chaos (well, okay, *not* mathematical chaos, but it just doesn't behave as expected).
Tracking the normal vector of the plane "paddle" with a GUIText (Debug.Log or Unity Remote does not work yet), and it seems the ball just doesn't react to it (usually doesn't even bounce before losing touch!)
@paulius - unity's great and startlingly easy to pick up! i finally activated my pro trial, just started with it last week, after hours - already starting to fumble around and do... quasi-stuff with it!