Evil Podium

This Idea starts by pointing out the existence of a "speaker" technology that uses ultrasonics (produces sounds that cannot be heard). See the first link. The ultrasound interacts with the air in such a way that the air becomes the source of the sound -- more, a particular point in the air can be the source of the sound.

So, equip a podium with a hidden ultrasound speaker system, such that the ultrasound waves are aimed at the microphone(s) on the podium. Audible sound would be produced in the air just next to the microphone(s).

Your victim steps up to the podium to make a speech. He or she positions his or her mouth near the microphone(s) on the podium, and he or she has ears that are not near the microphone(s). When you activate your ultrasound beam, he or she will not be able to hear the sounds produced --but the microphone(s) on the podium will hear those sounds.

So, you have secretly recorded many prior speeches made by your victim, and have edited your recordings appropriately, into sound- bites you can individually select from your remote-control panel for the ultrasonic speaker system built into the podium. Whenever the person speaking pauses to take a breath, you have an opportunity to put additional words into his or her mouth -- and they will be his or her own words, too!