Today’s invention is another way to make use of the Brazil-nut effect (a vessel, containing two sizes of particle, when shaken causes the largest particles to rise to the surface).
In this case, the idea is to show a consumer of tablets when they had exceeded their use-by date.
A container of medicine in the form of (white) pills would also have a population of larger, colour contrasting (red) spheres added to it.
On purchase, the container would be shaken for a specified period and then placed beneath an electric toothbrush charger on a bathroom shelf (these vibrate regularly, all the time).
This would cause the pills and spheres gradually to separate (at a rate determined by their relative sizes).
After some weeks, the user would look in the jar, see only red spheres and realise that his or her pills were too old to be clinically effective.