yes, but my point is that anyone who already has reverse ssh tunnelling working with pubkey auth should (AFAIKj be able to take advntage of it regardless of your own experience, as long as all you do when processing "remote on" is to run ssh -R ... I can't think of a scenario where if your app ran that cmd on my phone, back to my own server, where it wouldn't use my existing, valid keys.

this is more a question for the guy enquiring whether it could use pub key than it is for you as the app developer - i just don't see why he'd need YOU to support pub key, as I think it will already be inherently supported by ssh itself as long as you config your phone & home ssh servers correctly? ... but I may have misunderstood (are you maybe calling ssh via a software library rather than as a straight shell coomand? If so, I guess that may allow you to force p/w auth only?)