Before the iHeartRadio app, before the Walkman, before the transistor radio, there was: The Radio Hat! Looks like it had an antenna, a speaker, and, no doubt, a battery. I can't imagine what the whole thing must have weighed. I wonder why it never caught on.
This video shows a dapper, up-to-date, on the cutting edge of technology, 1930s commuter listening to his radio hat on his way to work.
photo YouTube video