Location was the first "killer-tech" for smartphones, and innovators have found several ways to use it. For retail, apps exist to find nearby stores, provide coupons, and give directions to the front door. But once you enter the store, location-finding ceases to work. That's because your location is usually found by finding GPS satellites in they sky, and the store's roof blocks the signal. But it won't take technology long to solve that problem.

The first problem to solve is a lack of indoor maps. Navteq and others provide very accurate maps of the outdoors, enabling navigation for cars and pedestrians. Micello is building a business creating digital maps of indoor locations like malls, convention centers, office buildings. They have over 500 live maps, including maps of IKEA stores. They claim it took them only four hours to create a map of the Stanford Shopping Center in Palo Alto with its 1.4 million square feet and 140 retail stores.

And within stores, retailers are producing more accurate plan-o-grams. I'm always impressed watching demos of our space planning from AVT. It uses CAD software to allow you to walk the virtual store and see products on the shelves.

The second problem is being able to determine location inside the store so it can be overlayed on the map. There are several goals for this endeavor. Your smartphone might direct you straight to particular products, it might summon a sales associate to your location for immediate assistance, and it might send you coupons based on the aisle you're viewing.

Companies like Nearbuy, ZuluTime, and Skyhook are working to master indoor location using a combination of GPS signals, WiFi, and cell tower positioning to calculate a location. (Skyhook calls this WPS, as depicted in the chart.) Today they can usually hit 10 meters accuracy, but that number is improving all the time. When it gets inside 3 meters some the goals mentioned earlier will be in easy reach.

I for one can't wait until the time my iPhone leads me directly to the sprinkler heads in Lowes and Home Depot.