For interactive lectures microphones are often passed around the room or taken from person to person by a teach assistant (or equivalent). This often introduces delay into the process, making the interaction less smooth (and also wasting valuable education time). At the same time, almost everyone in a lecture theatre is probably carrying a microphone on them - on their smartphone. All we need is an app that allows us to connect.
How would such a system work? The lecturer could provide a QR code at the beginning of the lecture allowing all participants to log in to that particular lecture. When the participant wants to ask a question, they press a button on the phone and a notification is sent to the lecturer's computer. The lecturer can then choose to take the question, which makes that participant's mic live (connected to the PA system of the lecture theatre via wifi). Likewise, when the lecturer asks a question, participants can press a button on their phone to respond - will the first respondent's mic becoming live. Additionally, the lecturer can pick a student at random from the set logged in if no-one is forthcoming in answering the questions.