One way to get at this wasted power is the “Batteriser” – it’s a very thin cylinder that contains electronics to boost the voltage from your batteries – making a 1.5V battery useable down to 0.6V.
The Batteriser is a sleeve that you slide your disposable batteries into. It has miniaturized circuitry that maintains 1.5V at the terminals, until the batteries are completely drained. The device is re-usable and should be able to fit in most devices.
I think the next phase should be deploying this technology into the devices themselves. This could also increase the useful battery life of rechargeable batteries as well.
They plan to have it in the market this fall and are targeting 4 for $10.