We've been experimenting with this model too, as "write once, run anywhere" is very tempting for business logic, but those platforms have traditionally fallen down when it comes to UI and other native functions (e.g. alarms, sensors, etc). So far, it's proving very do-able. Non-trivial in some areas such as multi-threading, but a lot more practical than replicating the same logic across Android, iOS, and web.

The individual talks' videos aren't up yet but you can probably find it here: https://youtu.be/nfb6lDnvtKQ?t=13852