Next to 2 new "The Other Half", Jolla also releases the official developer kit for those who want to create an own Jolla cover.

The PDF is quiet detailed including information about electrical interfaces, I2C bus, NFC connectivity and several software APIs for controlling various The Other Half hardware resources.
This support is very unique in the world of mobile phones and let Jolla users create whatever they want or are able to do - great unlike move Jolla!
Download developer kit here