I haven't had much success searching for this. I'm developing an Android Things application that will connect to a user phone to do certain things. I want to use this for delivering app updates as well.
So far, my crude searches on this have just discussed OTA via the Console and thus internet.
My gut has said that I could just build this - I could have a new version of the APK, transfer it to my device via bluetooth, and then just have the device copy it over the old one and reboot. But, not sure. I was hoping maybe there was an API for this and I'm just not wise enough to know how to find it via the searches.