beyond the unihertz existing, I think that there's probably an interesting space for a device that works on the idea of intermittent internet (i.e. wifi)

Offline maps being a big one that you could maybe "just" do. If you really need to get the device online pull out your phone.

Though I feel like there's loads of stuff that are on LTE etc. Just... they're real companies doing real things and not people hacking together one-offs. Think agtech, vending machines etc.