Shashank Priya and his team's emergency onboard charger draws energy from the piezoelectric force generated by your fingertips clicking the keypad, your voice - or just by giving the phone a good old shake.
The researchers experimented with zinc oxide, a common piezoelectric material, to see how well it converts vibrations from sound and pressure waves into energy to power a phone.
They subjected the material to sound waves of 100 decibels, which made the material vibrate and produce an electrical current at about 50 millivolts. In a cellphone, the piezoelectric material would be mounted below the keys and convert mechanical vibrations into energy that could be stored for later use.
It wouldn't produce a great deal of power - certainly not nearly enough to continuously operate a phone - but would be sufficient for an emergency situation, said Priya.
"In an emergency you could just shake your cellphone for a few minutes to get enough power to make this one important call," New Scientist quoted him as saying.