I ride a motorcycle with a full face helmet and gloves.  The gloves do not allow you to press the home button on the iphone despite it being mounted right in front of you on the handlebar.  The bluetooth mic at my chin is impossible to reach with the gloves on and even if you cram your hand under the chin guard you would be guessing and fumbling around trying to press the tiny mic (activate Siri) button).

From a safety perspective, the rider should be able to keep both hands on the controls and simply say "Hey Siri" into the bluetooth mic inside the helmet and have Siri activate.  I have been searching the internet looking for this capability and this forum is all I have so far found.  Sadly, no answer appears to be available to activate an "always listening" bluetooth mic.  

Google assistant apparently can do this from what I have read, but users complain that the headset/mic battery is dead in less than 2 hours.  I would prefer 2 hours of safe riding as a start.