I've got a few of these now. They work great for refrigerators, freezers and kegerators. (Which would make them fine for a fermentation chamber as well).
The top range of them is 158F which means they won't work for a mash tun or sparge water, plus their probe is a bit smaller than a standard one so it doesn't fit a thermowell very good. Also, their accuracy is +/- 2 degrees.
If you got the Celsius model and want to make it into Fahrenheit, it looks like you might be able to re-solder a jumper inside. If you want to pop the back off a Celsius model to compare to a Fahrenheit one, let me know and I'll post a pic of mine.
These are good cheap thermometers, just not for the brewing process.