I worked at Interval Research (yet another Palo Alto lab) in the mid/late 90s on a large project (and if it had completed and worked out, would have led to a proper IoT without the crap, maybe) in which we use Smalltalk all the way down to the custom hardware. A few hundred lines of C and assembler tucked away in a corner, but interrupts and processes were all handled in Smalltalk.

It was fun. It could have been great.