Charge your mobile during working on it or playing games

hey some days before i read a post in which a idea for mobile charging by pressing it is given i want to modify that idea. Now a days mobiles are used are screen touch but my openion is regarding the keypad mobiles. Can we use a pizoelectric like material to made the pcb of mobiles so by this we get a thing is that when we press any key to give it input i send a input to it but the pressure on switch or key also produce a some short of voltage which may be used to charge the battery. In that post the guy say that we should make a area on mobile by pressing of which we produce electricity or voltage and charge the battery.but in my way we should merge that special area beneath the keypad of mobile so we don't require additional time to charge it or do this exercise. and if we are sucessfull then the mobile discharging problem will be short out upto a great extent.and the battery life will increases.The coolest thing is that if a person uses mobile more then its battery backup will also greator and its a great help for game lovers on mobile.
so friends is this possible and if it does then pls do this or give suggestions how can we modify this.