I've heard of people going to straight pipes, or having their muffer converted to a "muffler" (Ie having the baffles taken out of it). Supposedly it doesn't make the car very much louder, and removes the muffler restriction.
I looked at their website, and I don't think that would fit an insight. I haven't measured it, but I don't think the exhaust system is anywhere near the 2 1/4" in/out size of the car version of this.
Also, (and I'm speculating here), that whatever is happening in that thing requires a lot of heat and exhaust flow to do its magic, neither of which you'd get from an insight. Most of their tests are on high performance or high displacement cars.
One thing I'd call shenanigans on is that they ran the tests at 5000 feet of elevation
http://www.aero-turbine.com/benefits/. That seems rather odd to me, as most cars are leaned out at that altitude. They ran another test on methanol fuel.
Also, typically increased hp and torque = less mpg. I wasn't able to find any charts on mpg, just hp and torque.