I thought the only options for Apple products were the Apple iOS SDK, and HTML5 a distant second if it's even supported.
My knowledge is a few years old, but at that time the smart device choices were Apple vs Android ... Android unfortunately had a lot of variations between manufacturers, making Apple products the first choice to capture the biggest chunk of the market with one API. HTML5 was supposed to solve all of the world's API programming issues, but I haven't heard much more about it in the last few years.
I just took a look on the Apple website and it seems to be focused only on it's SDK. There is the mentione of creating a "Universal App", but in Apple-speak that means an app that will run on an iPhone, iPad, and iPod Touch ... ha!