We've all been there. Waiting for a long time for a doctor is no fun. That is unless you have a handheld device. A person in possession of a smart phone does not "wait" because they are engaged in tasks (okay, games). We are doing something else (somewhat productive or at least entertaining) right up until the time the doctor calls us in.
A box of Smarties is the toddler/preschooler handheld device equivalent. It is a highly effective distraction tool that keeps everyone going for the majority of the time before they need to go in.
A Smarties' box is a multifunctional implement that encourages rattling (glare right back at all those annoyed onlookers or try to be as impervious as possible), a puzzle (how do you open it up without help?) and of course a piece by piece snack that can take a nice long time to finish. Adults have smart phones, kids have Smarties.