Play music over wired headphones. Connect to peripherals that use the original wide connector. Talk with dongles that communicate over the headphone port, like those credit card readers.
Oh shit. I totally didn't realize that Apple royally boned everyone using Square readers.
Did they though? Seems like magnetic stripe readers in general are on their way out.
Modern iPhones can play music over wired headphones! Sure, not all wired headphones. But then again, the original iPhone can't play music over all wired headphones either.
Apple has adapters so a modern iPhone can play music over wired headphones or connect to 30pin devices. These probably also work with these credit card readers. Or get a new one after 10 years, they’re only $50.