Kirby, the Dorkfood controller ran around $100 and can be used with any roaster, slow cooker, etc. (up to 1,000 watts if memory serves), as long as it has a regular analog type controller (it won't work with digitally controlled cookers). It utilizes a PID controller, so once the water is up to temp it holds an extremely accurate temperature with very minute temp swings (usually +/- 1°). The first time I used it for finishing sausages, and saw how accurately it held temp, I was hooked!
It was one of the first sous-vide controllers available for home use. They are sadly out of business now as there are too many circulator type sous-vide controlers, such as the Anova, available at great prices.
I appreciate what you're saying in your above post, and already have everything I need to do a similar setup to what your friend has done because that was my original plan. I
may actually get it setup here soon
.
Before getting the DorkFood controller, I tried using a roaster without a controller, and while it works in a pinch, it's much harder to maintain a precise temperature. But with the controller, and being able to dial it in at a precise 155°, the method I described above has worked well for over five years, for many sausages (large and small diameter) with zero fat-outs. Smaller diameter sausages, taken off the smoker at around 135° -140°, are usually finished in the 155° bath within 15 minutes or so. And larger diameter (hog casings) are finished within about 20 minutes, so stirring every few minutes is no big deal.
In all honesty it's probably a moot point, anyway. With circulator type sous-vide controllers available now for under $100, THAT is the way to go, and probably what I'll be upgrading to before long.
BTW... Here's a small batch of larger diameter smoked sausage (hog casing) being finished with the roaster and controller.