No, but cbp could have a k9 at any bottleneck they want and those dogs read their partners body language, so if they are a racist idiot it might alert on excessive melanin providing probable cause. Assuming they didn't just train it to alert on command. And if it alerts yeah they can demand to search your phone. I don't hear about it getting used, but that could be because they are careful not to use it on anyone who might start a case that could get it ruled unconstitutional. They openly use it where they think there is actually smuggling.