I'm not sure if this is the same as "Mobile Passport", but Mobile Passport allows you to complete the kiosk information on your phone and in most airports (IAD/

I'm not sure if this is the same as "Mobile Passport", but Mobile Passport allows you to complete the kiosk information on your phone and in most airports (IAD/BWI tested) if you tell the usher (non-CBP employee with the airport) that you're doing Mobile Passport, they let you skip to the immigration counter bypassing several long lines.