https://adamdrake.com/big-data-small-machine.html
A big benefit for doing everything on-device is that a lot of privacy concerns can be mitigated. I also agree that sending data to a server for learning is an option, and the privacy problems can be addressed with something like client-side feature hashing as I mention in:
https://adamdrake.com/scalable-machine-learning-with-fully-a...
However, doing that in a very power-conscious environment dose pose difficulties with radio usage, which is comparatively power hungry. It's probably a case-by-case situation.
It may make sense now, but not having to power up the radio for every decision is a huge gain, as lined out in the article. The current model of dumb (as in ML) devices is coming to an end, see also CoreML from Apple.
Inference is much less energy intensive and could be done on small chips.
Regardless, I'm not as certain as the author about the future of ML on small devices. Some ML models are huge and needs to be updated frequently, therefore there is little sense in downloading those to small devices. In such cases, it makes much more sense to send feature data to a remote server that can generate a prediction within milliseconds, and then transmit that prediction back to the device.