The ear radio is of course one of the many "hindrances" that are imposed upon indivduals who are not mediocre in order to level them in terms of their ability with everybody else. Note what the text tells us about this ear radio at the beginning of the story:
And George, while his intelligence was way above normal, had a little mental handicap radio in his ear. He was required by law to wear it at all times. It was tuned to a government transmitter. Every twenty seconds or so, the transmitter would send out some sharp noise to keep people like George from taking unfair advantage of their brains.
Throughout the story, at various points, George is distracted by a bewildering array of sudden, sharp noises that act to prevent him taking advantage of his superior intelligence in this way. As such, the ear radio represents a hindrance or another strategy of achieving equality.
A modern day equivalent is rather difficult to come up with, as fortunately we do not live in a world that is so insistent upon achieving equality, whatever the price. However, I am thinking a cell phone might be a good equivalent. Most people seem to have them permanently strapped to their ear, and it does seem to impact their overall intelligence and ability to relate to other people that they may see face to face.