I don't do yoga, but I do note during kung fu classes. I find it fairly easy to come with vocabulary to describe the moves and the sensations of the moves (turning, kicking, clenching, pushing, swinging, punching, pressure, tension, etc...). The vocabulary for feeling tone, emotions, thoughts and other senses are largely the same as when sitting, but with a different emphasis (there's a lot more looking & listening).
I find that noting helps to keep me from daydreaming and contemplating dinner while doing repetitive moves and static postures that I'm extremely used to doing. The feedback loop is improved attention, leading to noticing more technical mistakes and areas for improvement, leading to actual improvements and satisfaction (or noticing of dissatisfaction interfering with my practice), leading to being motivated to pay more attention and being more present. It results in a fairly good session of noting while doing a more intense session of exercise than I otherwise would have done with improvements in moves where I'd been stagnating or that I had aversion to (such as a particularly brutal squat that we do).
I assume that any repetitive exercise is as easy to model. It's a bit of an effort at first, but once you get the vocabulary down pat for your particular exercise, it will become very easy and habitual to note, at which point it's worth examining what you're glossing over and missing. Since the pace is slower and there's more emphasis on static postures, I assume that it should be easier to note while doing yoga, pilates or some similar exercise.
FWIW, yoga will probably do good things for your back and help you avoid the lower back pain that meditators tend to end up with after a few years of sitting practice combined with office work. I'm considering taking up yoga to deal with that.
