I have a pair of Bose Hearphones, cheaper than hearing aids.
I only use it at meetings (which I don't go to because of Corona) and to watch Law & Order on TV (because all the other shows are loud enough but it's not.)
The device consists of a yoke with the on/off button, two leds, a charging jack, and the battery, and two earbuds.
Each earbud has 3 microphones, they say**, and when being put in my ears they sometimes squeal, which the manual says is normal. Feedback, I guess.
The question is, when both buds are no longer in my ears, the device waits a while and turns off.
How does it know that the earbuds are no longer in my ears?
**And it can be set to amplify what's in front, what's in front and to the sides, and sounds from all diretions, so it probably does have 3 mikes per ear.
As good as this might sound, there are one or two other competitors. Before I bought this I googled but didn't find them. One will play the last 10 seconds back again, and iirc will play the last 10 seconds at reduced speed. I'd feel real bad that I didn't get that one, except I probably wouldn't use those things, at least at a lecture. If I were in the market, I'd look at the others before buying any of them.