While I welcome such a feature, I get the impression that it is not as simple as needing a portable device with a mic.  Sonos has stated that the device needs to have consistent reliable properties, which is why android devices, which don’t have the required mic consistency. Perhaps what they have not stated is the processing power, which a phone would have, that the Roam or Move would not have.  Maybe it just can record the audio and your Sonos app on phone can do the processing, don’t know.  Point is, it seems that there likely are other factors involved that we don’t know about.  For one thing, Sonos is having to go through the development effort of tweaking and testing trueplay every time Apple comes out with an idevice.

BTW, a plug in speaker like the One would not work since trueplay requires that you move the mic about the room.  The Roam and Move have autotrueplay, which is a less effective version of trueplay, but still much better than no tuning at all in my opinion.  I would be in fair of autotrueplay for the plug in speakers as well.

I’m not saying it’s straightforward, but it definitely seems doable:

• Android devices don’t have the required mic consistency, but Sonos devices do (and it’s an even more controlled hardware environment than iOS).
• I don’t know if processing power is a problem, but if they implemented (offline) Voice Control system, this should be possible as well. Or maybe just record and send it to the Sonos app, as you suggested.
• This would make it a good sales argument for Sonos Roam and Move.

Anyway, this is a feature request for us (poor) Android users. Having to borrow an iPhone from our friends is quite sad now...