Several years ago power meters were only used by a few elite athletes. Now they are becoming more common, and nearly everyone uses a heart rate monitor.
But does it matter that the power meter doesn't show you what's going on inside your body (only what your body puts out) or that a heart rate monitor has some deficiencies (e.g. lags behind physical effort)?
Don't get me wrong -- these are both great tools for training and for managing your efforts, and like many athletes, I'm addicted to mine. However, for better insight into your performance, you need a combination of indicators. And that is where the muscle oygen monitors/sensors come in.
Here is a great article by kennakata of The Athletic Time Machine that explains the benefits of muscle oxygenation and how to make it work for you.