This might be a feature request or some automation I don’t know how to set up on my own.
I’d like to be able to yell at my laptop/iPad/iPhone and have Siri switch from ERG to Resistance and back. I’m usually in a spot where my hands are tied up, and it’s extra effort to reach for the keyboard (and there are too many steps on the mobile version).
My workaround right now is a Bluetooth keyboard mounted on a music stand next to my bike so I have an easier reach to “T” and the arrow keys.
Siri integration isn’t available at the moment, and your workaround is probably the most effective strategy for the time being. However, I think this is a nice idea, so I will pass this on to the team!
This won’t work with an Ipad or Iphone, but I use this little satellite keypad to run some autohotkey scripts to do just this and more.
I like it better than voice control because a) I ride at 5AM and my voice sounds loud at 5AM and b) the fans sometimes make it hard for google assistant to hear me properly.
Not too different than your bluetooth keyboard, but some additional automation.
I don’t have Siri or Alexa (anyway TECH FAIL!!! Americans React “Amazon Alexa Can’t Understand Scottish Accent” - YouTube) but its a neat idea if it doesnae (doesn’t) confuse ERG for Aggh 
