In the videos from the "article", the pool guard jumped in while the person is still trying to get above the water. They never lose consciousness and get away with a scare.

This system is "trained to detect people under-water" and in the demo it only starts beeping after about 6 seconds of no movement while the person is on the bottom of the pool. So the person first has to get exhausted, sink, stop moving, and then the system catches on that something is wrong. I guess if you get oxygen into the person fast enough, they can make a full recovery, but in the context of a pool this should not replace lifeguards. At home, this is better than nothing, though I wonder if actual (near-)drownings would go up or down because of the sense of security.

Edit: the About page confirms it:

> Without air in your lungs, your body sinks [...] For children, irreversible damage to the brain tissues typically starts to occur after about 4-5 minutes without oxygen, (for adults it is after about 3-4 minutes). $product detects when a person sinks, meaning seconds after she or he stopped breathing

Detecting people that have gotten lungs full of water and are unconscious at the bottom of a pool is better than not detecting that, but it doesn't sound like pool guard or proper parenting can be replaced just yet, even if it might be a helpful last-resort aid.