I also thought this was a sales pitch, especially since you've made more than one post about this.
Do I find hard nipples attractive? No. Do I want to see someone's nipples through their shirt? No. Do I want people to see my nipples through my clothing? No.
I've seen pasties that were in the shape of hard nipples and they are meant to be seen through the shirt, etc, and I think the idea is just absurd. Even if a product could naturally do that, I'm not interested at all.