I mostly use public transit. sometimes my bus wait is for 10-20 minutes. sometimes i do standing at that time, instead of nothing at all or being tired and waiting. or sometimes i even do standing at work, when i have no work to do. it is really the only kind of training i can do at certain times is just standing. if it was acceptable to fight people or use a heavy bag at work or at the bus stop, i would. haha
i think this is a good time for standing, when you have nothing else you can do.
also if you have to stand out in the winter, simple standing will keep your whole body warm easily.