Weird. I just wired up an STC-1000 to an outlet over the weekend to hook up to a crock pot.
As Debaser42 says, it's a temperature controller, not a PID controller, so it's not going to hold at a constant temperature. Depending on the variance you set on the STC-1000, it will go lower than you want it to be, and then once the crockpot reaches temperature, the outside of the crock is already warmer than you want the liquid to be, which means it's going to vary quite a bit. Leave the variance low and your crockpot on low (provided you don't need it to be warmer than 93C), and it won't be too bad. You probably won't cook the perfect medium-rare-all-the-way-through steak, but it'll be pretty close.
I did my inaugural run on country-style pork ribs by starting them in a Weber kettle grill with some applewood, and let them cook enough to get nice and brown on the outside and for some of the fat to render. While that was going on I had a crock of water heating up to 60C. I brought the ribs in, let them cool a bit, and put enough water in the sink so I could submerge some ziplock bags in the water and put the cuts of meat in bags and sealed them. They cooked all afternoon like that, and they were delicious, smoky, and tender. Today the temperature controller is watching a pot of milk that'll be turned into yogurt overnight.
As far as the food-in-plastic thing goes, all I can say is this: if the idea of food cooked in bags grosses you out, avoid chain restaurants.