Due to the architecture of the SDK solution - JS library, add-on, native client - there can only really be one instance of the SDK registered at a time...this makes it tricky to use it across multiple web sites.
About the best approach I've seen is to implement the SDK/soft-phone core functionality as a custom browser add-on (e.g. a Chrome extension) that can then be used/referenced from any/all pages. (Unfortunately I don't have any working samples of such..)