How to launch Siri from nrf51?

Alright, I have searched high and low and been unable to find a simple answer to this question. It must be possible for the nrf51 to launch Siri on an iPhone, I have seen product using it mention this as a feature. But I cannot find out the way to do it.

Anyone know how? Is it a special HID media key? Or some other profile? All I want to do is launch Siri, not interact with it, so the equivalent of holding the iPhone home button.