Craig Hockenberry (IconFactory, Twitteriffic, Tot) just released a free iOS font manager called Fontcase, and discusses it here.
(Note: for years I’ve used the free AnyFont app, which I also recommend, and I paid for the $1.99 unlock of public-domain[?] fonts.)
nicey 
I’ve been using AnyFont forever too, solid app.
AnyFont always let you transfer over your own fonts, but the huge free-font unlock was so convenient, and I wanted to support the developer, so I purchased it. And I use it all the time without thinking. I like to do long-form writing with a monospace font and the included Fira Mono is a pleasant option. (On my Mac I use the similar Fira Code Mono.)