CBP has backed an app for mobile devices that may help speed up things to clear US passport control. Initially pilot is at ATL, but I've already got the app even as ATL is an airport I rarely use as a US POE.
https://www.cbp.gov/travel/us-citizens/mobile-passport-control
From the announcement press release:
Mobile Passport Control (MPC) will allow eligible travelers to submit their passport information and customs declaration form via a smartphone or tablet prior to CBP inspection. This first-of-its-kind app was developed by Airside Mobile and Airports Council International-North America (ACI-NA) in partnership with CBP as part of a pilot program at the Hartsfield-Jackson Atlanta International Airport. IPhone and iPad users can download the app for free from Apple’s App Store.
ATL is the pilot.
To find the app in the Apple App Store, search for Airside or Airside Mobile. That should help get you to Mobile Passport - Officially authorized app for download.
So now I can use Global Entry kiosks, Automated Passport Control kiosks, traditional staffed station processing, or "Mobile Passport Control". It's nice to see CBP jumping in on the experimentation game if only to speed things up.