Welcome to the forum! To run a Vault you need storage space and bandwidth, but to just run a client and connect to the network, a lot less resources are needed. @dirvine talked about a Client on a cellphone using low resources, or indeed a Raspberry Pi. No reason why it couldn’t be smaller than that I guess. Although I don’t know of examples on the little devices you showed.
As a smart washing machine I still need to send data into the Safe network and have it stored there. I may also want to accept instructions from my owner via the maidsafe network. That traffic/data would need to be paid for? So the device has to generate enough safecoin to cover it’s runnning costs?
I guess the owner could be generating them elsewhere, but it would be better if each device was paying it’s own way?
I can add I agree with @anon40790172 that simple devices could run a vault. There will be a gap though. If something runs on Windows or a Linux based OS, it is relatively straightforward (though not necessarily feasible) to run a vault and/or client on a simple device. Once you get to something even simpler, it becomes theoretically possible but would need specialist work that would be beyond most developers capability, and may never happen.
So far on small ARM devices - yes. I run on beaglebone, looking deeper at stm32 and other cortex M boards as well. Arduino is less likely though. Cortex M is really micro-controller only Cortex - A for sure no prob, an interesting one will be the cortex R for Iot type devices. If anyone was tinkering there then we would be onto something. For this I am following rust zinc as an easy way forward (stm32 OK there for basic micro-controller apps) zinc will make it easy if it gets to cortex R for sure.,