The technique of using light to transmit sound has been around for over half a century.. although it's more commonly used as a microphone rather than a speaker.

https://en.wikipedia.org/wiki/Laser_microphone

A microphone is just a reverse speaker. For example, if you plug your earbuds into an audio input port, you can use them as a microphone.

This is all relatively basic, just not obvious to most people.

I am not sure it is really as basic and obvious as you imply. The comparison between the "reversibility" of laser speakers/microphones and the reversibility of normal speakers/microphones is a bit off, in my opinion. For starters, laser microphones do not use the photoacoustic effect[1] that the device described relies upon. Whereas the reversibility of normal speakers/microphones is because both devices use the same physical process. That it's possible to build a microphone using lasers and to build a long-range sound generating device using a laser doesn't imply it's obvious (or even possible) to do so for any given audio production or recording technique. E.g., if I can generate audio using a flickering lightbulb, it is not clear that a flickering lightbulb can be used as a microphone.

[1]: https://en.wikipedia.org/wiki/Photoacoustic_effect

They also point out they can use this to bypass security and open "smart-locks".. this is slightly more concerning than just buying hand sanitizer.. I wouldn't be caught dead with one of these smart-lock devices, but I have friends who aren't so cautious.

I have owned several smart locks and every single one has required a secret passcode to actually unlock via a smart assistant. Working backwards, the real threat if they didn't do that is just someone shouting through the window.

I forget if it was this article or not but someone mentioned that a few of the smart locks that do have secret codes don't rate limit them, so, in theory, they could brute force a pin code or password.

I guess the idea is that they think nobody is going to sit there and shout pin codes until it unlocks?

I own a smart lock and my Google home device will only lock the door. You can't ask Google to unlock it.

I don't use a smart assistant, but I think some people use them with smart locks ("unlock the back door").

Alexa doesn't let you unlock, you can only check status and lock it.

Until a vulnerability is discovered.

How about telling their smart speaker to complete a task that might be connected to more sensitive things, like unlocking a door, opening a garage door?

Money is important to people.

Because it's about more than just buying stuff. Potentially you could say "Hey Siri, transfer all of my Monero coin to XYZ address".