There are various forms of in-store marketing: coupons on shelves, end caps, on floor, in-store video, POS screens and so on. But here's something really valuable and fresh: Aisle411. We discovered it through the Voxeo blog.
The company works with retailers (big boxes) to help consumers locate products on store shelves -- within the store. I don't have a dollar figure but I know from personal experience that this is a problem: consumer wants to buy something but can't find it on the shelf. The salesperson is either ignorant, not available or otherwise unmotivated and so the consumer winds up frustrated ("I guess it's not here"). How many sales are lost because somebody can't find the item they're seeking and give up?
Consumers are prompted to call 1-877-AISLE411 by an in-store display. They're taken through a DA-like menu (store, city, item) and ultimately directed to the aisle where the item is normally stocked ("sippy cups are in aisle three"). The system also gives stores the opportunity to promote other items (upsell related items) and specials of one sort or another.
It's pretty interesting. Here's a quick demo with call flow.