I was going to pose this question, then did some research and think I figured it out. So hope this helps or if I have it wrong let me know.

When coming home more than not we miss our connecting flight trying to get through customs in ATL. It's is nice that the car rental tram takes you past a stop where there is a choice of 3 hotels if you have to stay the night, but obviously not preferable. So the last couple years we've been going through CLT. This year the cheaper flights take us through ATL and I remember one year in the past we were faced with huge custom lines and surely would have missed our connect had it not been for an airport worker that keyed us into a line where you download a passport app that literally let us skip to the front of the line. So I went looking for that app again to have it on the ready. I think that app was Airside Mobile Passport. Some googling is telling me that Customs and Border Patrol has put out their own app that supersedes Airsides called Mobile Passport Control, MPC.

Does that all sound right? Does anyone else do this and does it still get you to bypass the lines?