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How do you track someone’s indoor location down to the meter?

Boston-based startup ByteLight thinks the answer is to stick a microchip in LED lightbulbs and then use its software and your smartphone’s camera to detect invisible-to-the-naked-eye lighting pulses from those bulbs, thereby revealing your exact whereabouts.

Got that?

Well, it doesn’t really matter. All you need to know is that if you’re in a participating store and using its app, ByteLight knows where you are and how to find that pair of shoes you saw for sale online. It can also let retailers send you mobile coupons based on precisely where you’re standing, regardless of whether you’re using an iPhone or an Android device.

And, as of today, it now has a further $3 million in funding to help further its mission of turning you into a mappable shopping dot.

ByteLight’s Series A round comes on the back of its $1.25 million seed funding that it raised in October 2012 from VantagePoint Capital Partners. The new investors include Flywheel Ventures, Motorola Solutions Venture Capital, the eCoast Angel Network, Sand Hill Angels, and Google developer advocate Don Dodge, a big believer in indoor location, a market expected to be worth $4 billion by 2018.

Because that opportunity is so large, however, ByteLight will find itself in for some stiff competition. Apple, which earlier this year spent $20 million to acquire indoor GPS startup WiFiSlam, is set to get into the game in a big way, with its recently launched iBeacon feature opening up the potential to turn iPhones into mobile retail transmitters with pin-point accuracy. Google, meanwhile, continues its efforts to improve indoor mapping, and Nokia is leading an alliance of 20 companies to develop and deploy high-accuracy indoor positioning based on Bluetooth low energy.

On the startup side, Aisle411 closed a $6.3 million round of financing in September to help it create digital maps of physical stores, and just a couple of weeks ago offline-online retail marketing company Nomi announced $10 million in Series A funding.

ByteLight co-founder and CEO Dan Ryan says his company is piloting its technology with three big-name retailers, but he won’t disclose who exactly they are. The eight-person company will be using the money to hire more people for its engineering team as it continues to build out the product.