I bought them at SuperTarget, but first saw them at Costco. There's some added sugar in the Target ones, but they're still blueberries, and concentrated ones at that.
I'd bet you could do them in a dehydrator. In fact, here's a link (at least on how long it takes) to do it -
http://www.logicsouth.com/~lcoble/jg.../dryfruit.html
If it works for you, let me know. I'm kinda interested in getting on of those.