Yes, 100%. For instance, my Pixel Watch measures and logs my heart rate every second. Though I doubt that something as volatile as a user's heart rate has any significant value to advertisers, over the treasure trove of other, more reliable data points they already have collected on any given user.

People act like every single facet of their lives has some intrinsic advertising value, when really it's only specific things that advertisers are interested in. They want to know your habits; what sites you go to, what physical spaces you frequently visit, what sort of content you consume, what you spend your money on, etc. Those are metrics that advertisers can capitalize on to make sure that they're serving you ads that you're more likely to engage with.

Biometric data, on the other hand, is basically worthless. Even if we pretend that Google is using my heart rate data from my Fitbit profile for advertisements, that data gives Google basically nothing to work with. Did my heart rate fluctuate because of an ad I saw? Or did it fluctuate because I stood up and walked to the kitchen while a YouTube ad was playing? There's no easy way to discern this sort of nuance, making it effectively useless for advertising purposes.

Maybe if we lived in a more cyberpunk world where advertisers could access things like our serotonin or dopamine levels, and could link that directly to things we're actively seeing/hearing, that would be worthwhile to advertisers, because then they could actually know how something you interacted with affected your brain chemistry. But as it stands right now, heart rate by itself is little more than junk data.