The guy who's filling his notepad with drawings in the meeting? The coworker whose leg is running like a jackhammer? It's possibly more than boredom or caffeine powering them. Some researchers suggest such activities actually help focus on a task at hand.

Researching the spectrum of Attention Deficit Hyperactivity Disorders, Fraser Smith at edexpat.com, a site focused on education of expatriate children, came across some surprising ideas from researchers about the nature of nervous movements. It covers pen tapping, idle drawing, and all the other stuff you've done at one time or another during a long phone call:

The theory is that nobody can focus 100% of their working memory and attention to a single task, there is always a little bit of floating attention keeping a watchful eye on the surroundings. This floating attention is a safety feature that probably dates back to prehistoric times when the ability to focus 100% on a single task was not entirely desirable and would result in a person missing the large ravenous beast hiding in the bushes, the result being that the ravenous beast would become somewhat less ravenous

... Researchers have found that one way that ADHD children cope with these distractions is to unconsciously give their floating attention a nice mindless task, like fidgeting, swinging and fiddling to keep it occupied allowing the rest of their working memory to get on with the task at hand, learning, uninterrupted.

It might be hard to consciously make yourself start fidgeting to pay attention, but it does give you some sympathy for those who seemingly can't help themselves. Maybe they're just honing in on something that you're a bit more apathetic about.