mojoPortal does not have a comprehensive set of web services, so if you are looking to make native UI that replicates all existing features you are not going to find services for that included.
We do have an AuthenticationService and a RoleService, which could probably be used for authenticating users and determining their roles from a native IOs app. You could build your own web services for whatever custom functionality you are trying to build.
We also have support for metaweblog api which can be used for making blog posts and as of recent code can also be used for creating and editing cms pages with html content feature. We use it to support Windows Live Writer but you could use that api from a custom app. Our implementation of metaweblog api is extended with a few extra wordpress api methods that are supported by Live Writer, this is how pages can be edited since the standard metaweblog api is just for blog posts. These extensions ar eonlyin th elatest code in our source code repository at the moment.
Hope that helps,
Joe