We've built and use https://thumbsignin.com (TSI for short) on our intranet apps for simple (i.e. one step and secure) authentication using our mobile phones. ThumbSignin is FIDO certified and we've worked to add more authentication means for enterprises as time passed (TSI is 2 years old now I think).

Disclosure: I work for Pramati Technologies which developed and owns ThumbSignin.