Access the domain variable inside custom services module

I've written a custom services module that is used by both android and iphone clients. Each of these clients have their own domain, android and iphone respectively.

Now, I've never had a reason to know which was making requests to the module until now (I have to give different stream URLs for different clients). So, my question is how do I access the domain being used in the request within my services module?

Any and all help greatly appreciated.

Thanks!