I don't believe that there is a mobile app for kbin nor do I think you should expect one anytime soon unless you make it yourself. Kbin is still extremely early in active development.
However, if you run Chrome or Firefox on your phone, they both have an option to "install" a page as a webapp, which works remarkably well. It's what I've been using and frankly I don't have much in the way of complaints that might be fixed by a dedicated app. It feels like it is one.