Last millisecond targeting has been on the tip of my tongue ? and that of millions of marketers ? since early last year. It is a powerful concept: marketers need to deliver spot-on relevant consumer experiences in a millisecond or risk losing the visitor, possibly for good. Every moment has an almost instantaneous decision that follows, be it buying, converting or abandoning. 

So, for marketers, every second ? and fraction of a second ? counts in today?s omnichannel ecosystem. 

Enter mobile. 

Last millisecond still exists, certainly, but the overwhelming convergence of mobile and in-store ? consumers browsing on their smartphones, then shopping at a bricks-and-mortar location, mobile couponing or showrooming ? gives the concept an entirely new context. 

Today, we cannot just focus on the last millisecond of a consumer?s digital journey, but, instead, have to be on point when it comes to the ?last inch? of mobile/in-store engagement, too. 

I would argue that the stakes are even higher in this scenario: lose her in the last-inch context, and she walks out the physical and the virtual door. 

The biggest game changers in the space today are beacon- and other Bluetooth-based technologies. 

The 2014 Adobe Mobile Marketing Survey found that 18 percent of brands are currently using beacons, with nearly two in five planning to integrate it in the next 12 months. 

The power of microlocation is the real deal: shopper marketing agency inMarket says beacon-using brand partners have seen product interactions increase by 19 times.  

With the holiday season in full steam, consumers will likely see even more brands hopping on the geofencing bandwagon. 

Lord & Taylor, Macy?s and GameStop are already on board, pushing everything from massive same-day discounts for passers-by to gamified in-store experiences and interactive product details and reviews. They will face the challenge of getting consumers to flip on their notoriously battery power-zapping Bluetooth when they enter or are near the store, but it is not insurmountable. 

It all goes back to relevance, and the fulfilled promise of personalized experiences is usually all it takes. I will gladly switch on Bluetooth as I enter your store if it means I am getting real value ? you, the marketer, just need to train me to do it, unprompted. 

The same goes for application engagement. 

For those brands not implementing beacon technology, existing apps can be a great way to leverage microlocation and deliver relevant experiences and offers in real-time. Get consumers to open the app when they enter your location or vicinity with that same relevance promise. 

I have to buy groceries for my family: how great would it be to get a discount on something I was planning the purchase, or for a product that is complementary to what is already in my cart? That is the kind of meaningful moment that propels consumers from ?shopper? to ?loyalist.? 

Services such as shopkick, SnipSnap and RetailMeNot are poised to dominate a huge piece of this last-inch targeting landscape, as each can deftly push customized offers or coupons via their own apps, targeting consumers based on a host of specifications. 

But many insiders argue it is retailers who are in a position to gain maximum traction. Consumers, they argue, want more direct brand engagement, which are seen as more relevant, more powerful and more in tune ? something to think about, especially if you have already got an app in play. 

Stop & Shop is a great example of a brand which is doing this right. It launched ScanIt! in 2007 and, last year, a companion app. 

What started as a way to increase consumer convenience ? a relevant benefit unto itself ? became an effective, efficient way to push personalized offers to shoppers as they moved through the store. 

Grab bread, ham and cheese, and maybe an offer for chips or pickles pops up as you are passing those aisles. Or get an instant coupon for a brand of whole wheat pasta you have not tried before because, week after week, you have purchased whole wheat pasta. Its service-provider partner, Modiv Media, estimates the system saves shoppers, on average, 10?15 minutes and $7 per basket.  

And, of course, you cannot talk about apps and geofencing without considering the push/pull debate. 

Chances are you, as a consumer, have received a push notification from an app, be it breaking news, travel updates or an alert that your cousin posted more vacation pictures in the family photo stream. They are true ?pushes? ? you didn?t do anything in that moment but, even so, content was pushed to you via your mobile device. Invasive? Possibly. 

Again, if it is related to something I am looking for, thinking about or doing right now, then fantastic ? that is relevant, and I am happy to have it. 

With standard geolocation technology, that is all more possible than ever ? think a one-day sale at a store I am passing or physically in, or a push that a restaurant just a few feet away still has space for dinnertime walk-ins. 

Like Bluetooth, these push notifications rest on consumers opting in to receive when they download your app, or switching their settings later. 

Some brands have no issues with this: Uber, for example, has high notification acceptance rates, since knowing my car is on the way or just arriving is of immense value. That cousin with the photo stream? He is all over Facebook, Instagram and Twitter, too. Maybe I do need all of those alerts. 

Create relevant reasons to opt in and consumers gladly will. 

Inundate consumers with useless or generic content, and you will be no better than Cousin Judy?s vacation albums. 

There is also the pull side of this. Think shoppers, in store with the retailer?s app on their phone. Relevance delivery happens within that app, like the buzzed-about Target Cartwheel. 

Cartwheel enables consumers to self-select relevant offers and discounts, with the app becoming the last millisecond pull as the consumer shops. 

Because she is already engaged with the Target brand and already physically in the store, the pull experience becomes incredibly organic and relevant than even the best push strategy. 

LAST MILLISECOND matters, but the convergence of in-store and mobile has created a new piece of the puzzle: last-inch targeting. 

Fail to engage, turn and deliver relevance on a dime, and consumers will find it somewhere else. 

The brand, product, offer and experience are just a step or a click away. But make that meaningful connection, and the brand and the consumer win in conversion, satisfaction and long-term loyalty. And that is always relevant.