Yes. I use one. It works great to get the must up to temp and fermentation started. Watch your temp because you may have to unplug it for a day or two during max fermentation then plug it back in for the rest of the week. They say not to use it more then 7 days.
I'm not a wine guy, and I ferment my beer in Sanke kegs, but I goggled it. This link says it'll fit on 7.5 gallon buckets. I'm not sure what the difference is to a 7.9 gallon bucket, since I've never seen one.
BTW, I lived in Terre Haute, IN for a while, then Shelbyville, IN for a while.