TSA has already been doing tests at LAX T4.

When I went through in December, they were scanning the boarding passes of all travelers. Have also heard it was being done at ORD T3 (AA) - but I have not been through that checkpoint lately.

At LAX T4, it resulted in long, slow moving lines. Not sure if they're still doing this. BP scanner was built into the TDC podium.

SDF_Traveler