Interesting app but what then is the purpose of Global Entry??

It sounds like you create a profile/pic in the app and then scan it on arrival...

No DHS interview, no need for fingerprints on file (and used for ID at the kiosks), save $100

What is the difference from the self-service passport scanners now available at some airports??

Doesn't sound too secure unless I am missing something. Huge potential for using the app of another person if your looks are similar