In the next debate, when Mr. Trump has the occasion to shake Hillary’s hand, he should do a quick pat down with his left hand on her back where the suspected device would be. I know distasteful patting her down seems, but he was half way there in this last debate
Trump patted her back at the end of the debate.
Watch in the video at the end, she walks over to him to shake his hand, he shakes her hand and the other hand goes on her back.