Best way: Using phone with expansion module as operator console

I’m looking for the best way to use an IP phone with an expansion module, such as the Aastra 57i with 560m, as an operator console.

I suspect what I need to implement is “Asterisk presence,” but I don’t really know how it works, how to implement it, or if the Aastra 571 supports it.

Any help will be appreciated.