Morse code was the standard for single-channel binary communication for centuries. It's still used in some applications. Obviously it's not particularly useful

Morse code was the standard for single-channel binary communication for centuries. It's still used in some applications. Obviously it's not particularly useful for communication with an untrained user, but it's a pretty proven method for single channel communication with a good balance of complexity and data transmission rates. I suppose its use in an application ultimately depends entirely on what you're trying to communicate and why you're constrained to 1 bit.