[m-p-3]

I see those as a "gateway-drug" to the world of tinkering, there are so many lesser known (and less powerful computationally-wise) that are better fits for simple devices like the ESP and some wireless communication chips like LoRa and DASH7 that can really expand the stuff you can achieve. And these chips are low-powered enough that you can combine them with a battery and a decent solar panel to make them self-sufficient.

Like you said, imagination is the limiting factor, and I enjoy seeing these kinds of projects popping up in the wild.