Are there alternative to REST to access hosted data for an iOS App?
Basic operations are create an account, store prefernces, store user generated content (data + media), access data + computed result (computation happens on the server).
Are there any simpler alternative to using REST (Restify + Nodejs) for auth and access?
As far as an API goes, I don't think it gets much simpler than a clean RESTful interface.
For Auth, you could always avoid doing it yourself and lean on an existing service people may already have like Facebook or Open ID.
In then end, the code you'll write to handle those is probably pretty close to what you'd write if you did your own authorization.