Love this.... I used 5-4-3-2-1 with a fourth grade class last semester. There were too many students to do jumping jacks, so we shook out each hand then each foot. So, it was a 5-5-5-5, 4-4-4-4-, 3-3-3-3....you get the picture. They loved it, and it helped them get refocused.
Brain Breaks are always good to have an a class especially on days when you may be introducing a new topic that you know students may have a hard time with from past experience. A brain break would be good so that the students will not get to overwhelmed.