I've been bored recently, and made a set of Bluetooth speakers using an old helmet intercom system. Now I can listen to the music on my iPhone without it giving me an "Accessory not supported" message.
The whole job took a morning and works well for me.
I have a container full of duplicates, triplicates, and cheap tools that have had a better life. Never throw anything away. You will find a use for it one day.