If you HAVE TO stand and wait why not use your time wisely? Instead of straining your eyes on your smart phone for the hundredth time that day or slouching un-intentionally on the joints of your body, why not practice your Mountain pose, a.k.a "Tadasana"? Unlike many of the people pictured here, the yoga posture would effectively engage your lower body muscles, stack your spine efficiently, and allow time and better positioning for diaphragmatic breathing.
Just in case you need a refresher from yoga class: Position your ankles just under your hip bones. Press down firmly into the ground with all four corners of each foot and engage your leg muscles all the way up to the hips. Position your pelvis in neutral so you can feel the abdominals and gluteals engaged, (again another thing you learned in yoga class), and picture your long, healthy spine as you lift from the crown of the head. Your shoulders are stacked over your hips and your ears are directly over your shoulders/not forward from the shoulders. No one will notice your slight shifts and muscular engagement. No one may even notice your slow, even, long breath patterns in and out of the nose. You will feel better. You will be training the body and the brain to get the most use of your idle time. Way to go!