I turned my ancient car stereo into a Bluetooth-powered modern stereo with an amazing $30 device

My partner and I just bought a car, against my better logic as a New Yorker. It's this glorious old Volvo station wagon:

Buying a 13-year-old car means buying a 13-year-old car stereo, as I recently learned. And a 13-year-old car stereo is very likely to mean no Bluetooth, and no auxiliary port for wires.

The only way to play music in my new (old) car is to play CDs (!!) or to listen to the radio (!!).

In 2005, there wasn't even an iPhone yet! In 2018, my phone is a supercomputer that plays music over Bluetooth or auxiliary wire.

So, how to solve this problem of old technology meeting new technology? As it turns out, there's an amazingly simple, elegant way to solve this.