I get what you are all saying about finding stillness through activity but I think there's something amazing about also being able to find stillness inside yourself, especially during those times when you can't jump into a physical activity when you need to.
With your yoga backround, maybe something like chakra breathing would be easy for you to learn & use. I like this type of exercise because (after practice) it's something I can use to get centered quickly & use anywhere, anytime. It feels somewhat physical to me because I focus on the chakra colors & energies as I breathe through them; I find stillness in directing my energy toward moving my breath. It feels active, but it's also passive & I get 100% return on investment.
The steps at the bottom of this website kind of describe what I'm talking about
:
Opening the Central Column of Light - Reiki Webstore
Here's another, longer variation:
Keys for Doing Chakra Breathing Meditation Successfully