Police in Tokyo say they have found that English proficiency test examinees involved in suspected group cheating had been given miniature earphones and other devices prior to the test.

They suspect that there may be other collaborators in Japan in addition to a Chinese national arrested in relation to cheating on the Test of English for International Communication, or TOEIC. ……

They say they have learned that the examinees in question had been given earphones measuring 3 millimeters across, a pendant-type repeater and a video guide in advance. ……

Those are very tiny earphones (you can see one in the video around 0:45). I wonder if there are any electronics inside or if they are just tiny magnet balls driven by the pedant repeaters.