I think it's a matter of personal preference how you track it. If you want to track both mental and physical exercise, then I think it's fine to do, especially since you're not counting calories burned as part of the equation :)
"You may have a fresh start any moment you choose, for this thing that we call "failure" is not the falling down but the staying down." Mary Pickford
"No matter how slow you go, you are still lapping everybody on the couch."
I do regular cardio and strength training (and stretching), but have been considering adding meditation to my exercise groupings. I believe it's good mental exercise and while not calorie burning, just as important as physical exercise.
Thoughts? I would be especially interested in hearing from a Spark Coach, but welcome other thoughts. I don't want to feel like I'm "cheating" on getting exercise points!