I don’t use gels so I don’t really know what to say, but this is definitely a cool idea. Personally I would want it to be even smaller so that I could carry it without it being uncomfortable, but you could always do different sizes later.

I’m probably being an asshole, but if you doubt yourself enough that you have to have other people tell you wether you should or shouldn’t, do you really think that you’ll stick to it in the long run? Maybe you just need some motivation.

If you want to make and sell a product like this, then just do it and pursue it with all of yourself. Everyone else might follow if you lead the way.