Here is what I have been able to do as a work around for always listening ok Google.
You will need s voice, Google now, and tasker.
1. Configure s voice to respond to wake commands. I use "ok google" at this point you can make it whatever you want.
2. In Google settings disable OK Google detection, (really need to do this if you use s voice with hotword ok google, if not your mic will have conflicts) but enable hands free. ( we will be using s voice wake to trigger google voice search via tasker)
3. Tasker create profile and task
Profile: Variable Set %WIN, Value S Voice
Task: 1. Go home 2. Launch app Voice search
Done
What will now happen is SVoice is programmed to respond to your wake command, it will wake causing tasker to follow its programming of going to home screen then launching voice search. Not a flawless fix but it works. Let me know if this helps anyone.