Can I connect One to a loudspeaker for teaching?

Definitely -- and just remember, it's all about the bass. Laptop speakers are completely useless. You won't hear a thing! Larger computer speakers with a fat sub-woofer are reasonably good in a smaller room, but it's probably a real nuisance having to provide them.

If your lecture hall has a stupendous PA system, that might work. We've seen Thinklabs stethoscopes used in front of live television audiences by a famous TV doctor.

In terms of connection, you can connect the One directly to self-powered loudspeakers like computer speakers, and you can easily connect it into a PA system. We recommend using a loudspeaker with good bass and a long extension cable
to avoid acoustic feedback. This speaker is great for bedside use.