Wireless power. And while early lab experiments have been able to “beam” electricity a few feet to power a light bulb, the day when our laptops and cell phones can charge without having to plug them in to a wall socket still seems decades in the future.

Nokia, however, has taken another baby step in that direction with the invention of a cell phone that recharges itself using a unique system: It harvests ambient radio waves from the air, and turns that energy into usable power. Enough, at least, to keep a cell phone from running out of juice.

Mind you, harvesting ambient electromagnetic energy is never going to offer enough electricity to power your whole house or office, but it just might be enough to keep a cell phone alive and kicking. Currently Nokia is able to harvest all of 5 milliwatts from the air; the goal is to increase that to 20 milliwatts in the short term and 50 milliwatts down the line. That wouldn’t be enough to keep the phone alive during an active call, but would be enough to slowly recharge the cell phone battery while it’s in standby mode, theoretically offering infinite power — provided you’re not stuck deep underground where radio waves can’t penetrate.

Nokia says it hopes to commercialize the technology in three to five years.