All you need to do is create a contact and in the Web site field put the code for the system preference. for example.
Contact name is Bluetooth and the Web address is prefs:root=General&path=Bluetooth
Then activate Siri and say "Bluetooth" the contact card will open with a clickable link right to the Bluetooth settings.
It's not the much-sought-after "Siri, turn off Bluetooth" feature we've all been hoping for, but it's better than the nothing we have now.
bamf-hacker has also posted the URL schemes for other popular Settings, so hit the link below and get the details!