All that goes on there is an evaporating tray of water and wet bulb temperature sensors (finicky to measure accurately). Imagine an environment similar to a dishwasher or rather, a sauna, where you play not just with the temperature but also the humidity by controlling the steam bath.

The Chinese commercial ones I am referring to use a fill valve with a float (not dissimilar to a toilet tank) to replenish the water from the evaporating tray found at the bottom of the oven. So might get away with an analog circuit.. I digress..

Instead of keeping your food in a plastic bag and recirculating the water through a heating element to keep the temperature you are just constantly boiling water and releasing steam so the entire oven cavity settles at an exact temperature AND humidity level. Hope I didn't bungle that explanation too much.

Anyway GM probably has super fancy home ovens of this nature for $10,000 a premium home gamer version of the sort of thing restaurants/fancy-hotels use. The pros simply front load food trays into them like this: https://www.youtube.com/watch?v=3cfll7tUcuA

https://www.youtube.com/watch?v=AJb9cYXo-4g

The Anova thing is basically a tiny toy version of that.