When you go to the grocery store, chances are you find yourself hunting for at least a couple of items on your list. Wouldn't it be easier if your smart phone could just give you turn-by-turn directions to that elusive can of tomato paste or bunch of cilantro, and maybe even offer you a discount on yogurt, too?

That's the idea behind ByteLight, a Cambridge, Massachusetts-based startup founded by Dan Ryan and Aaron Ganick. ByteLight aims to use LED bulbs—which will fit into standard bulb sockets—as indoor positioning tools for apps that help people navigate places such as museums, hospitals, and stores, and offer deals targeted to a person's location.

Accurate indoor navigation is currently lacking. While GPS is good for finding your way outdoors, it doesn't work as well inside. And technologies being used for indoor positioning, such as Wi-Fi, aren't accurate enough, Ryan and Ganick say.

Ryan and Ganick feel confident they're in the right space at the right time: there's not only been a boom in location-based services, but also in smart-phone apps such as Foursquare or Shopkick that use these services. Meanwhile, LEDs are increasingly popular as replacements for traditional lightbulbs (due to their energy efficiency and long life span).

ByteLight grew out of the National Science Foundation-funded Smart Lighting Engineering Research Center at Boston University, which Ganick and Ryan, both 24, took part in as electrical engineering undergrads.

Initially, ByteLight focused on using LEDs to provide high-speed data communications—a technology referred to as Li-Fi. But Ryan and Ganick felt their technology was better suited to helping people find their way around large indoor spaces.

Here's how it might work: you're in a department store that has replaced a number of its traditional lightbulbs with ByteLights. The lights, flickering faster than the eye can see, would emit a signal to passing smart phones. Your phone would read the signal through its camera, which would direct the smart phone to pull up a deal offering a discount on a shirt on a nearby rack.