CP Global Function

If I wanted to have a function that was globally available while developing add-ons etc, what is the best way to handle that? I can drop a helper in the expressionengine/helpers folder, and autoload it, but I would really like it to be a third_party/add-on so that when I upgrade it still exists. The key is I want it to be available to any add-on folder etc.

Thanks in advance!

-Todd