Raspberry Pi TV HAT
Transmit audio over FM
For the ham radio enthusiasts, great piece of software called rpitx that can turn pi into a FM transmitter. Link to software here.
There is a specific use case in the new version - replay captured audio. Useful for automating doorbells etc that use RF.
Composite video with raspberry pi
Before this week, I was not aware that 3.5mm connector in the raspberry pi is capable of outputing video in addition to audio.
In order to do so, use need a special 4-pole 3.5 mm connector. Not all connectors are the same.