Note that border searches of electronic devices are extremely rare overall. There were some statistics from CBP implying a base rate lower than 1 in 10,000 (I think lower than 1 in 100,000) border crossings.
I do know two people who have experienced them as a result of the government taking a personal interest in them, so it's certainly not impossible. However, it's not a common experience.
I've personally experienced searches of my suitcases about four times in about 100 U.S. border crossings (as a U.S. citizen, but the people performing or directing those searches generally didn't know my citizenship status), and zero electronic device searches.
I bet they are very reliable. Just look at the immigration hall of the average international US airport and you'll quickly realize that it is literally impossible for even a fraction of the people going through there to be physically searched. Of course this applies only to the average visitor and I'm sure you can significantly increase your changes by being the the "right" line of work - but from my experience and the people I know and work with, being in "IT" in general is not enough to get you searched.
But why would that be legal? The device is owned by the individual. No judge signed any warrant search for the device. I can do what I want with my device - that is a basic right of property. Imagine if border guards seize money willy-nilly.
Because I was curious about this exact same question, I did some looking on this last night.
Case law on this seemingly requires some nexus to a border. In Almeida-Sanchez v US[0], a Mexican citizen was stopped while driving on an east-west road that was near the border but that didn't connect to the border. The marijuana that was found in his car was excluded because there was no proof he was actually crossing a border, just near it.
So I'd expect, under a functioning legal system, a warrant would be required to search your phone if you landed in JFK on a flight from Altoona.
Edit: Not on the border, btw. Just people travelling inside US. I guess it was their mistake to carry cash instead of getting a bank check or something.
I do know two people who have experienced them as a result of the government taking a personal interest in them, so it's certainly not impossible. However, it's not a common experience.
I've personally experienced searches of my suitcases about four times in about 100 U.S. border crossings (as a U.S. citizen, but the people performing or directing those searches generally didn't know my citizenship status), and zero electronic device searches.