It was the one feature I liked on Android – though, as ever, that meant it was on one Android phone somewhere – and it was then the one thing that might make me jailbreak my iPhone.

OkSiri… makes Siri listen all the time. No pressing a button and waiting a mo before speaking to Siri, it is listening all the time. And specifically it is listening for a phrase such as “OK, Siri” that it then recognises as its cue to work.
This I Might Jailbreak For – William Gallagher (1 June 2014)

Glad I didn’t bother now. Maybe the one WWDC announcement that most grabbed me was HeySiri. (I don’t like that name any more than I do OkSiri, but.) It is exactly what that OkSiri is, except it’s official, it will work.