Comment by carpenecopinum

Besides being a great project, this device reminds me a lot of the Technifant (https://technifant.de) which, under the hood, is similarly simple. The "hats" that you put on the Technifant contain a cheap USB thumb drive with the contacts soldered to a magnetic connector. All the audio is stored locally on the hat itself, and you can even add your own MP3 files with a cable provided by the manufacturer.