Paul Flanigan starts with "How do you market to someone who isn't there?" and goes on to say:
It is a challenge that marketers face: Customers get their information from everywhere except where the item in question is sold. The sales cycle is now in the hands of the customer, and she will dictate when, where, why, and how she’ll acquire her purchase. Smart marketers will innovate, trying new experiences that achieve the timeless and known practice of keeping her in the store so she will spend her money there.
I met Paul at the iQmetrix Wireless Summit and he's been a great source of knowledge about all things digital signage and interactive retail (check out his presentation on Consumer Trends and the Influence of Interactive Retail).
The quote above really resonates with me as I'm digging into this space - info from everywhere and customer experience above all.
I confess, I'm really fascinated by this online to offline space. You'll see me blogging more about interactive retail and the convergence of online information and offline, brick-and-mortar sales. Location based services fit in here, as does more data / analytics around those physical sales.
If you're looking for more of a walkthrough of this connected shopping experience, check out London, UK-based design agency Spotspot - the slides on their front page summarize it well.