Hey guys, just saw this. I've never used one for mixing photography or lab chemicals, but magnetic stirrers are a big thing in Homebrewing for making yeast starters. Basically, the stirrer constantly aerates the yeast starter so you have a large initial pitch into the unfermented beer.
There are a lot people who have started making magnetic stirrers because the lab grade ones are either too expensive or too hard to find for the average homebrewer. Most that I know of are not heated. If you are looking for a good (cheap) stirrer homebrew yeast stirrers are a great place to start.
I have one from Stir Starters. It works great for my purposes. I use a 2000mL erlenmeyer flask for making starters with this device. I think he also has instructions on a DIY version on the website as well.