First of all, in December we released a new tool called Objective Sharpie that can automatically bind Objective-C libraries into C#:
http://forums.xamarin.com/categories/ObjectiveSharpie
If you're skilled enough to build the Objective-C library, then you'll be able to use Objective Sharpie to create a C# binding. We also have docs on doing this for Java on developer.xamarin.com.
Some of our customers don't have the time or skill to do this themselves, and so we've recently created a bindings team that wraps third-party native libraries for our customers. Many of these end up published on http://components.xamarin.com/ (there are over 300 components now). But some of them we can't immediately publish because we need to get permission from the original library author to redistribute their library. This is especially true for commercial SDKs. But if you contact us directly, we might be able to give you something.
We also do custom bindings through our support team. This is something that unfortunately we haven't made very obvious. But you can just email support@xamarin.com and we can create a binding for you.
Like I said, this is an area we're pretty focused on. If you have any feedback, please feel free to let me know directly: nat@xamarin.com.
But when are you gonna let us use Xamarin Studio on Linux?
To target the full range of mobile devices, one has to have Windows, a Mac, or both anyway. So there doesn't seem to be much advantage to supporting development on Linux.
I don't see any options that come close to solving this. Xamarin is not native to either iOS or Android. RoboVM (the one i work on) can cheat, as we only need to solve it for iOS, Android comes for free. React Native has no clear path for accessing 3rd party libs at all yet. Whatever they can come up with will be further complicated by the fact that the JS engine is single threaded.
I've often been surprised at how easy it is to create bindings to libraries written in Obj-C even if no one else has before. Usually it requires extracting the compiled library from the framework, and then translating each declaration from the library's header into the C# binding definition. In many cases it's a couple of hours work (or less).
That said, libraries that are provided as source files, with the instructions "just copy them into your project," can be incredibly frustrating. Our designer would love to use github.com/MengTo/Spring but I have yet to find a way to use it in Xamarin easily.