The reserve tank
When I learned about motorcycles as a kid, I was introduced to the concept of the "reserve tank." I use it in quotes because it is not, in fact, a separate gas tank hidden somewhere on the bike — rather, it's an intake tube that rests lower inside the main (and only) tank than the main intake. Its lower position allows the rider to capture those last few drops of gas that the main intake cannot. A flip of a switch somewhere on the engine selects the reserve, which gives you just enough oomph to reach a gas station or your destination, whichever comes first.
I grew up thinking that it was a ridiculously silly concept. Why not just have one intake? Who are you fooling? Well, there are two answers: the practical answer is that motorcycles didn't have gas gauges when the concept of the reserve tank was conceived, so when your engine died (ostensibly because you miscalculated how many miles you could go on a tank) you knew exactly how much further you could go on reserve. The psychological factor, though, is just as important: the act of flipping the reserve switch is a very tangible thing. It forces you to recognize and acknowledge that you're almost out of gas. It imparts you with a sense of urgency.
And I got to thinking today: why not do this on phones? And I don't mean some lame software toggle in the phone's settings menu — I mean, let's really do this. Give me a physical switch underneath the battery cover, something I can get to in a time of crisis when my phone's teetering on death's door and I need an extra 45-60 minutes of standby. Go ahead and cordon off a couple hundred milliamp-hours worth of battery that can only be accessed when I flip that toggle, especially now that stock lithium-ion polymer batteries regularly offer 1,800mAh or more.
Generally speaking, I find that I adapt my usage patterns to however much battery life each phone I'm using offers (within reason), and I'd become accustomed to using a phone with that switch in the "main" position 99 percent of the time. Who wants to tear off their battery cover on a daily basis? But it'd be that other one percent — those moments of need — when I'd be thanking my lucky stars. "Oh wait, I have a reserve switch!" I'd exclaim, wide-eyed, to the people around me. Suddenly, I've got enough juice to make that last call, send that last text message, look up that last destination in Google Maps. And more importantly, the physical motion of flipping that switch puts it front and center in my mind that I need to focus on finding a charger or be okay with going phoneless for a while.
Image credit: k.bunch (eBay)