It's actually very possible and we'd love to see it as well. Steemit can incorporate the Airbitz Javascript SDK onto the website, and users could "login" using the Airbitz mobile app. This would allow Airbitz accounts to also contain Steemit keys. The same architecture that secures bitcoin in the Airbitz wallet can also secure your Steemit keys. Complete with PIN login, password recovery, One-Touch 2FA, etc.
Think of it as SingleSignOn for blockchain apps but unlike signing in with Google/FB, with Airbitz it's fully private, zero-knowledge client-side encrypted.
You should be seeing some cool announcements about this in the coming month.
RE: I'm Paul Puey - CEO and Co-founder of Airbitz