Hello Gabriel Beauchamp,
As XMLHttpRequest object is limited to only current domain, one possible solution will be to use local webservice to call local proxy class which in turn calls the remote webservice.
For example, lets suppose you have a webpage(A) which should call a webservice B (located in different domain).
Therefore you should create a local webservice(C) which calls remote webservice B. Then from webpage A you can call the local proxy webservice(C).
the Telerik team