This is interesting.

There are a few issues with the initial design, which shouldn’t bar it from sale.

1. Cultural acceptance. It’s silly. So were Bluetooth earpieces when they came out, but did become a small status symbol. So you’re spot on that they could be marketed better.
2. This one is a bigger issue IMO, you cant roll up the hat without impairing the Bluetooth earpiece. People’s ears get cold, and the easiest way to solve that is to roll up the bottom of your beanie to provide an extra layer of warmth. I’m assuming, with this beanie, if you do that, the speaker sounds muffled? You could potentially put another hole in the fabric at the top, but part of what makes hats warm is the lack of air circulation. In short, if it gets really cold out, people might choose a warmer hat, making this hat only viable during moderately cold weather.
3. This is an extension of the previous issue, the effective temp you’d wear this beanie (I’m going with below 40-60 deg F depending on the person.) You can look at weather data for global locations and probably pick areas where people wear hats like this (most likely 15–60 F with low windchill, really just a giant guess on my part,) and then market this hat in those locations. But for the rest of the year, it kind of sits on the shelf. As you know with tech, the product lifecycle is incredibly fast. By next year, there will be a newer better $25 headset beanie, and the previous customer experience will be, “well, it just sat on my shelf for most of the time, plus I wore a different hat when it got really cold, and in the summer, since I don’t use Bluetooth earpieces, I had to buy one, or didn’t have one… too much wardrobe choice, argh!”
4. Accidental washing? Yes you can remove the earpiece, but if you don’t, and it’s on, you can ruin the circuit.
5. This customer review is also hilarious (paraphrased), and a standard issue with Bluetooth: “I returned 2 of the 3 beanies I bought for my family to wear during outdoor workouts together. The “feel” of the beanies is very nice. However, when the hats are worn within close proximity (yards away from each other), the Bluetooth in the hats competes with each other and they lose connection.”
6. There are other companies online selling the exact same idea for less. Is it as nice? Probably not.

That said, I’ve never used one, and it sounds like your experience was pretty transformative. The company has also nailed the price point, so it can at least make its way through impulse purchases and gas stations (again no shame in that.) It also looks nice.

It would be interesting to see if these take off, and a good marketing campaign could definitely make the difference for this company.