RANCHO PALOS VERDES, Calif.--Meredith Perry and Nora Dweck, two freshly minted University of Pennsylvania graduates, were at the exclusive D9 tech conference this week showing off their compelling technology demo: Ultrasonic power transfer.

uBeam, the company they created around their tech, uses sounds waves beyond the range of human (and dog) hearing to transmit power. In a proof-of-concept demo (see video), Perry was able to move 5 volts at 50 milliamps, or a quarter of a watt, over three feet. She says that with custom components, not the off-the-shelf piezo speakers roughed into the tech demo, she'll be able to send 25 watts over ten feet.

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Engineers I talked to at D9 were skeptical that the science will scale up to this theoretical transfer wattage. There may also be challenges on health grounds, although Perry says that the transmission method is OSHA-approved and that similar technology is safely used in directed sound products. She also says that unlike microwaves, which can be used to transfer power but that are dangerous when absorbed by living tissue, uBeam ultrasound is reflected, not absorbed. But 25 watts is a lot of energy to pump through the air, and to be fair, Perry does say she got the idea for uBeam by reading about how sound waves (granted, of different frequencies) can be used as weapons.

Perry and Dweck have a good amount of work ahead of them. They need custom speakers and receivers to increase transfer capacity. They have to miniaturize their hardware so it's consumer-friendly. They need to develop a directional technology so the power sending unit can beam power to where it's needed, instead of to an entire room.

Rafe Needleman/CNET

And they need money for development, and then a go-to-market plan after that (sell uBeam gizmos to consumers, or license the technology to others?). This demo was the darling of D9, as it has it all: A team of two young, undiscovered, female entrepreneurs, a science-based product, and a gee-whiz solution to a problem everyone can at least identify with: nobody likes plugging in their devices. I saw a line of investors take an interest in this company at D9. Even DARPA chief Regina Dugan stopped by for a demo.

As cool as this tech is, I'm not sure the intended market--power distribution in coffee shops, classrooms, and so on, to power consumers' mobile devices--will actually exist when this technology is finally ready. Battery life of phones and tablets is going up, and new battery tech is also lowering the time it takes to charge a device. By the time uBeam technology hits the market, it may not present a cost-effective solution to the minor inconvenience of having to find a place to plug in a device for a quick power top-up.

Nonetheless, this is clever and innovative thinking, and I would expect it to find a practical application somewhere if it works as advertised. Just maybe not at Starbucks.