Alex Dunn and John Dagdelen have a smashing bet going: Who will break their phone first?

“I have the beefiest case money can buy,” says Mr. Dunn, 23 years old. “He walks around with a phone not in a case, which is kind of bonkers. I said, ‘Dude, you’re going to break your phone.”

Mr. Dagdelen says that will never happen. Like Nik Wallenda...