My version of a TLDR:
Spotpass is a wireless tech that would auto connect with other 3ds or Wii U systems that were in the immediate area albeit with a limited range. It was their way of having a social community. Sort of like how you might meet other people while walking around outside.
In the case of Spotpass, when you connected, it would show you the user's profile, their favorite games, etc. And in some cases for specific games it would provide special DLCs or content that cannot be found elsewhere.
Hence why we'd want to preserve that data since some DLC and other features are exclusive to Spotpass.
It does! It's on the Google Play store. https://play.google.com/store/apps/details?id=com.odysee.app