This technology is in a pretty early stage, so it's unlikely to hit the market anytime soon. For one thing, it requires photovoltaic cells to be either built into devices, or for third parties to offer add-ons that provide that functionality. And because you can't necessarily count on people to remember to put their phone down with the panels facing up, you need to build those photovoltaic cells into both sides—which means, yes, the side with the screen in it. That's a further limitation, as transparent panels are less efficient and require smartphone manufacturers to adopt them, which they're unlikely to do unless wireless power catches on...which is unlikely unless the manufacturers build in support for it. You see the problem.