Open Hotspots in Germany are incredibly rare (due to a just recently lifted law that made Hotspot providers liable for criminal activities commited over their connection). The use cases you described can be covered with an iPod Shuffle or similar MP3 player. The interesting part is really the mobile internet connection, which is hard/pricy to come by in Germany and probably other countries. Especially in rural areas you won't get a good enough connection for Spotify.
Another useful use case would be an emergency button for elderly people. Current devices are rather expensive and/or only work at home.
I don't think you need to use open hotspots - assuming you have your own WiFi at home, you can just do your syncing once you're back at home after your run. Also the core has GPS, which the iPod Shuffle doesn't.
I didn't find Germany's mobile internet too expensive, I was quite happy with Congstar prepaid when I was last over there. Certainly comparable with Australian mobile internet pricing. On the other hand, Australia now has free mobile Spotify streaming (on Optus), not sure if Congstar does.
> You can also use Core’s 4GB of built-in storage to access your favorite playlists, podcasts, and audiobooks.
> Core also works without a SIM card or cellular plan, using WiFi to sync offline music and workouts.