Hey mate, forgot to mention a few things:
Have a look at this, good example of what I was talking about.
In your OData, you'll pass that search criteria as a substringof filter as well, this way the OData implementation can search for various objects when it performs a GET request. So the OData will look something like /service/EntitySet?$filter=substringof('search criteria, something', AttributeName)
In the OData you can process the substring to help search for different entities in your search help dialog.