Does that mean that i got to do a mobile app? Do you think its worth it ?

It could potentially help with discoverability. As it stands, I’d imagine it takes a very particular sort of search query (either “open source fitness” in Google or “fitness” on GitHub) to have a chance at finding this. Unless your target audience is only the intersection of FOSS-advocates and fitness folks, you might be limiting adoption.

With that said, the website works just fine on my phone.