50, It appears they are developing this tech. for other portable devices as well.
AC Energy, Inc. (OTC: ACEN) is a publicly-traded company that has developed a remarkable mechanical battery charging system that enables mobile electronic devices to charge themselves as well as operate under power simultaneously. In other words, a cell phone or other similar portable electronic device (MP3 player, portable gaming system, PDA, pager, etc.) equipped with AC Energy technology could charge itself.