But have you wonder, you in a hurry, your battery still having charge around the mid bar. With mobile phone getting slimmer and more functions nowadays, battery life is shorter and chances of having a spare is likely to be. You went out, after a while, the bar gone into last bar!!! You suppose to meet someone and that person want to change location. After few calls later, you got cut off!!! You don't know ur friend mobile numbers and you could not contact him anymore. In the end, you will miss the appointment. So, will the 5 to 10 mins backup battery save your day?
If you think not, it's ok. Anyway, this idea can save life if you happen in a remoted area, even in local. You might be laughing at it that it is a joke for now but in the future, there might be this kind of phone surface and I guess it might save you some trouble. Think about it, you never expect what would be happening next.