So how, then, how are battery charger manufacturers able to market chargers that allow you to safely charge alkaline batteries? By carefully monitoring the charging process and building in intelligent sensors for preventing overcharging and over heating.
What makes a rechargeable battery rechargeable? The process is well explained in a Scientific American article: "One of the necessary conditions for a battery to be rechargeable is that the underlying chemical changes that occur during an electrical discharge from the cell must be efficiently reversed when an opposite electrical potential is applied across the cell." It must then be able to sustain this process efficiently and safely over many charging cycles for a battery to be labeled rechargeable.
While your typical alkaline battery has a reversible chemical process it performs more poorly with each charge. "In the case of the non rechargeable battery," writes Frank McLarnon in Scientific American, "when one attempts to recharge the battery by reversing the direction of electron current flow, at least one of the electrochemical oxidation-reduction reactions is not reversible." The result is a loss in charge and this assumes that a buildup of hydrogen gas in the reverse process hasn't caused the battery to rupture.
Its utility depends on how many alkaline batteries you have laying around to use with the $46 device. You're probably better off just gathering up your old AAs, taking them to be recycled and replacing them with NiMH rechargeables.