It’s an Android / iOS songbook app that helps you manage your song lyrics / chords and setlists. It’s a bit broader in scope than LivePrompter - displays PDF, plays backing tracks and video as well, networks multiple devices to follow a lead device, etc.
Pretty powerful, I’ll readily admit - I just didn’t like the handling for my core requirement (teleprompting for live usage), that’s why I built LivePrompter. But Set List Maker seems to have a pretty broad following.
It’s also got a “bigger brother” - BandHelper. That’s the all-singing, all-dancing app that aside from managing your songs and lyrics/chords does everything for the gigging musician, including scheduling, finance and stage plots - but it doesn’t brew coffee …