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It’s easy to track people carrying smartphones while they’re outdoors, where GPS works best, but indoors is another matter. This is why we’re increasingly seeing new sensor systems such as Apple(s aapl)’s iBeacon that can help stores follow their customers as they browse the shelves. Such systems offer unprecedented opportunities for hyper-personalized marketing, sent to the customer’s mobile device on the basis of where they’re standing.

But why install a separate system when a key feature of the store itself can be used to achieve the same end? That’s what Dutch tech firm Philips(s phg) is proposing: on Monday, the company unveiled a pilot of a connected in-store LED lighting system that can talk to a smartphone app using, well, light.

Yes, light can be used to set up a viable data channel, and Philips is combining that fact with the grid formation of in-store lighting to create a fairly ingenious positioning system. So rather than the phone establishing location on the basis of its proximity to a beacon, which usually involves Bluetooth, it does so by noting which lights on the grid are closest.

If active, the app can then receive alerts based on whatever the shopper is looking for – someone looking to cook a certain dish may find themselves directed to the ingredients and offered relevant coupons, for example.

According to Philips Lighting’s Gerben van der Lugt:

“The beauty of the system is that retailers do not have to invest in additional infrastructure to house, power and support location beacons for indoor positioning. The light fixtures themselves can communicate this information by virtue of their presence everywhere in the store.”

While Philips is a heavyweight in lighting technologies, it’s not the only one trying to use lighting as a means of communication. Boston startup ByteLight is selling light-based proximity beacons that link to a phone through its camera, but it’s eventually goal is turn a room’s lighting fixtures into a datacasting system.