Cameras at state lines... and follow any buses leaving polling stations to see if they cross state lines.
Just ideas.
I hope Trump’s campaign is ready for this. It is one thing to deal with a small number of states during the primaries at one time. But this is 120 million votes, and a majority will be cast on Election Day.
The turnpike in Kansas has live cameras at the toll booths available online. I wonder if other states have something similar.
You will see many coming up from Brownsville and Laredo in Texas loaded to the gills. They will probably be tour buses or Grehound buses (at the Greyhound facilities ) or the standard white government buses or vans. And they will probably have freshly minted bills in their possession. The Feds like to use Greyhound and other Mexican tour buses after they got busted using GS4 transports....