The great prize in advertising is getting as close as possible to the shopper when they are making the crucial retail decision. Being in their mind as the hand reaches out to the grocery shelf.
Over the years many ways have been tried, and as technology has become more sophisticated, the techniques have improved.
In the '70s and '80s numerous systems were devised. They featured clunky back-projected slide shows, and then TVs, perched at the ends of the aisles.
They were expensive and complicated, required a big initial investment followed by a lot of costly maintenance. Then inevitably there were the disputes - should they be allowed free access because they were promoting the sale of goods, or should the supermarkets take a cut of the advertising revenue?
In these days of flat screens and wi-fi, controlled by powerful computers, things are easier. Everywhere you go you'll find the in-store screens piping commercials at you - in supermarkets and hardware stores, retail centres and even your petrol pump.
One of the industry's early innovators in Melbourne, Alex Kaplan, eventually left the business but he still believes its effectiveness: "This is the point of purchase. The site is all-important. We researched the impact of these promotions and recorded sales increases, on products that were featured, of more than 25%. It was colossal."
Today, the explosion of smartphones has given the task a new dimension - now the customers can seek out and purchase their preferences themselves.
Some months ago I wrote about Korea's "supermarket in the subway" - pictures of products on the underground's walls that can be captured, and ordered, by a click on their QR ("quick response") codes.
Now IBM has taken smartphone technology into the store itself. Still in test it's dubbed "augmented reality" (AR?) at the company's research labs in Haifa, Israel.
Put simply, you can walk into a supermarket, point your phone at the shelves, and it will identify products with the qualities you prefer, from a questionnaire you will have filled in when you first registered.
Try and follow this: it will view the packs and goods through facial-recognition type processing and feed the information back to a huge database, presumably in the cloud, and the supermarket's own computer's list of its products.
Through optional connections with Facebook and other social networks you can see what your friends think about it, or you can alert them where you found it.
Now I've got to tell you, we're getting into the area of "too much information" for me here. I'm just not that obsessive. But it's an indication of where marketing is heading. And you always have the choice of leaving the phone in your pocket.
In planning your own business marketing, be very picky about the unlimited new technology on offer. Technical fashions constantly come and go, but I presume you intend your business to last.
Always remember that in advertising it will always be numbers that count - a few thousand Facebook clicks will never be more effective than a million TV viewers. By all means use the apps, but don't neglect the real drivers. You've still got to get the punters into the shop, in the first place.