One of the things I love about Zentangle is that it is so portable. I have a mini kit that I keep in my purse at all times. It doesn't hold much - but the beauty of Zentangle is that I don't need much.
I did this tile on the tray table of my airline seat. Quick and simple, using whatever tangles came to mind as I didn't have any books with me. It helped to pass the time and helped me ignore the occasional bumps of the plane. It was a lot more fun to do than what my seat mate was busy with. She had all sorts of boring looking work files on her computer.