Looks awesome, but I doubt it'll fit in my AA flashlights. 
http://theness.com/neurologicablog/index.php/batteriser-cool-tech-or-scam/
http://hardware.slashdot.org/story/15/06/08/1433243/debunking-the-batterisers-claims
If your AA flashlights are LED, they already have that circuit in them. That's all this is, a voltage boost driver, which sucks up the "long tail" (graphed out) of wasted amperage when the voltage drops below the threshold the battery operated device needs. So yes, it's "wasting" some of the battery capacity (generally as waste heat in the circuit) to keep the voltage up longer, but the maker's claims that it's capacity/mili-Amp-hours you're tossing in the trash are quite true.
In reality though, I don't think anything but the form-factor of the slip-on device is patentable, since there's tons of prior art done on voltage boost regulator circuits, and the risk to his business model with the device is that there's nothing stopping device manufacturers from incorporating "joule thief" circuits into TV remotes, Wii controllers, or whatever else is eating batteries. The only real barrier is the price margin of losing a few cents to do so, on something the consumer usually pays no attention to. Or, with the rather tiny IC's costing only a few pennies in bulk, Energizer, Eveready etc. incorporating them right into the skin and contact points of the battery and marketing them in a disposable form factor as both "green" and "longer lived".
LED flashlights are a somewhat competitive among themselves for brightness and runtime, plus often needing a forward voltage for the LED more than a common arrangement of cells in series provides, so the voltage boost driver at the expense of amperage/capacity has been common for a long time now.
The biggest fail is just the claims of 800% battery life. The math on that is shoddy beyond even grade-school.
Since most devices that are high-drain will have multiple batteries, like four of them in series etc, for 6v, and few consumer devices are so picky that they'll give up at 1.3 or even 1.2 v. IMO his product is "good enough" (I won't say revolultionary) at even a theoretical maximum of 50% extra life, down to maybe a more realistic 20%, that I'm not sure why he's pushing it into the snake-oil territory like this.
Even at 20%, assuming his volume price is right, the things pay for themselves pretty quickly. Not to mention putting a price on lost time or failures when that device death at the cell's last 20% happens and you don't have fresh batteries laying around.
He's better off making a run at it, and then getting picked up on licensing for the alkaline makers to cheap it out so much it can be incorporated into cells directly.
I think the worst part will be people forgetting they've clipped them onto batteries and tossing them. Much like how my wife and kids keep accidentally throwing away the NiMh's in our house.
