The sound waves produced a mild electrical current of about 50 millivolts. The average cell phone requires a few volts to operate, several times the power this technology can currently produce.
Wrong, so very wrong. Millivolts is not a unit of current, and volts is no unit of power. Nor is power current. I've seen journalists not understanding electrical units before, but never have I seen something quite so wrong as this.
I bet $1 Billion you didn't RTFA.
This is idle, GP didn't read the summary, probably didn't read the title. I know I didn't.
Never let someone who says it cannot be done interrupt the person who is doing it.