I seems like the monobjc is a low level bridge to the Cocoa API, and it states it works with Mac OSX. Since there is no mention of iOS, does this mean you cannot use this bridge to access touch based libraries?
It is technically possible to build the Monobjc bridge for iOS. The native code has received a lot of patches (https://github.com/Monobjc/monobjc/issues?page=1&state=closed) to enable this (except the FFI part, which still needs some work).
The hard point is that everything needs to be statically linked on iOS: you need to acquire a Mono license from Xamarin in order to redistribute the result as it cannot stay under the LGPL.