How to make an HTML5 video work on iPhone?

I have set up an ASP.NET MVC5 video upload-conversion-watching site, and I need it to function on iPhone. The two formats I support are webm and flv;

• I am NOT implementing .mp4 format due to the licensing requirements.

Is there an iPhone app, JavaScript library, or an extension that will allow the video to be played programmatically by my site, or an external iPhone application that can do it. The potential user base varies wildly in terms of technical experience, so any method will need to be relatively simple to follow. It would obviously be best if there were a way I could do it automatically, but I will take anything at this point.