As an afterthought, stove-top cooking could provide accurate temperatures for food as long as you used a meat thermometer. I have done such things on the stove top as pasturizing raw eggs for instance. I looked up the process and duplicatedd the temperatures and times by adjusting the flame on my gas stove, and closely monitoring the temperature. I used an electric thermometer with a probe and alarm to let me know if the desired liquid temperature raised too high. The same method would easily work with radiant cooktops or even better with induction cooktops. Ya just gotta be smarter than the pot you're cooking with to make this work. And I think the crowd who frequent this site are fairyly savvy folks.
Also, the reason for vacuum packing is that liquid is a much better conductor of heat than is air. That is, it transfers energy to and from food much more quickly. It also tends to stabilize temperatures as it is slower to heat and cool than is air. As the plastic is in complete contact with the food in the evacuated bag, the liquid can transfer its energy to the food more efficeintly that if the bag had air in it. This means that the food will come up to temperature faster, and maintain that temperature during minor fluctuations in energy applied to the cooking vessel.
As an experiment, I would think that hot water (boiling water) could be used to start the cooking process, even in sous vide, bringing the food up to temperature fast enough to prevent/inhibit microbial growth, and then, as the food approaches the desired final temperature, energy could be reduced to hold the food at the final temperature to insure that everything is done perfectly. The advantage of cooking in the desired temperature water is that there is no chance of overcooking the food. But if you are squeemish about critters growing in your slowly heating food, this is an alternate method that should aleviate that concern.
Seeeeeya; Goodweed of the North
Seeeeeeeeya; Goodweed of the North