There are reasons this hasn't been done before. I don't think it's a viable startup idea. Think about the capital you would need to even get something like this off the ground. Doing the AI API 'right' would require a supercomputer, if you take it far enough.
A guy can dream though. Maybe doing high-frequency trading would get you most of the way there.
IMHO, go for the niche: elsewhere in this thread Directed Edge was mentioned, and they are a good example of a business tackling a well-defined problem with exciting tools and techniques.
by implementing a web app that anyone could use (mobile or not), i also envisioned a sort of community/market place where people could post their data and do simple stuff and/or have experts try to tackle it for a service fee. and whatever algorithms came out of that would be made available for future data that has similar features. i recently came across a similar site. can't remember the name.
anyway, i know this is not necessarily a viable startup idea. and if it is, it's ultimately all about execution. i'm still dreaming though and was psyched google launched their predict api.
Not doing something because 'google might do it' is not a very good reason.