Once they have their own satellite-based cell network, they can take another stab at launching a mobile phone. The Amazon Fire2 phone will be able to use this proprietary network. Amazon could then go for entry into mobile markets by selling phones with data service included free, trying to become a third major mobile platform.
Alternately, Amazon is developing their Alexa-fronted Internet-of-Things (home automation, etc.). This network could serve those devices and make their setup easier. (No need to connect them to your wifi network. Amazon could claim their IoT is inherently safer because they control the entire network that they operate on, so your security camera won't get hacked. (Note that Amazon owns the Ring doorbell products.)
Alternately, Amazon is developing their Alexa-fronted Internet-of-Things (home automation, etc.). This network could serve those devices and make their setup easier. (No need to connect them to your wifi network. Amazon could claim their IoT is inherently safer because they control the entire network that they operate on, so your security camera won't get hacked. (Note that Amazon owns the Ring doorbell products.)