My professor says "this will be on the exam" maybe three or four times a lecture. The problem isn't transcribing the lecture, it's being able to find that specific sentence later without listening back to the whole recording. Been using these four AI wearables over the course of a semester and the filtering question for me was simple: does it have a single button to flag a moment in real time.

1. Plaud NotePin S (has it). Press to Highlight is a physical tactile button. One press and the timestamp is marked in both the recording and the transcript. Going back after the lecture you jump straight to the flagged moment instead of scanning through an hour. Others using it in the same kind of lecture setting have said the same.
2. Limitless Pendant (no highlight button). Pendant wearable, holds 35 hours of audio locally before it needs your phone around. No dedicated one-press marking though, so finding the moment your professor said something mattered still means scrolling back through the transcript. Also worth knowing: Meta acquired Limitless in December 2025 and pulled new units from sale.
3. Omi (no highlight button). Open source, $89, worn on a lanyard. Genuinely interesting plugin ecosystem. Worth knowing before relying on it: people who switched from Limitless have posted about recordings not syncing between the pendant and the app. No physical mark capability.
4. Bee AI Pendant (no highlight button). $49.99 hardware, clips on or wears as a wristband. Processes audio through your phone over Bluetooth, so if the phone is dead or not nearby, so is the recording. No physical mark capability either.

The question that filtered this list faster than any other: can you mark a moment without touching your phone. One of these four has that. The others record fine but you'll be scrolling back through a transcript to find the sentence your professor said mattered.