Smartphones are making retailers think again.

Asda, the UK supermarket chain owned by Walmart, launched a new “price guarantee” campaign a few weeks ago. This enables shoppers to access a price comparison website to check their overall spending during the store against leading competitors such as Tesco, J Sainsbury and Wm Morrison.

If a customer could have saved more elsewhere, the Asda site, operated by Mysupermarket.co.uk , will print out a coupon against future purchases to cover the difference, plus a penny.

According to Asda, about 15,000 people a day are now checking prices on the site, which covers about 70 per cent of Asda’s comparable products and demand had “surpassed expectations.”

Price comparison sites are not new. PriceGrabber, Shopzilla, and Yahoo Shopping have become an established part of the e-commerce landscape.  But with the increasing adoption of web-enabled smartphones, the new challenge for retailers is how to deal with consumers who are able to check prices not just at home, but in the store too.

According to surveys, the percentage of smartphone owners that check prices through their devices, is increasing significantly. The shopper’s ability to check prices while on the move is also being enhanced by a new generation of mobile phone-focused search engines applications.

Shopsavvy and RedLaser, for instance, deliver comparative pricing information, and information on nearby stores, to anyone who uses their mobile phone camera to take a picture of an item’s barcode.

Retailers are reacting in different ways to the realisation that their customers could walk out to buy a product more cheaply elsewhere. Some say that retailers will try to obfuscate this by offering products that others do not sell, such as exclusive private label goods, or by creating bundles of products.

There will also be an increasing readiness among retailers to match prices instantly. One strategy, called geo-fencing or wireless marketing, is now being tested by a handful of retailers in the US. In the near future, it will be possible to have those messages triggered by a search engine to persuade a customer to complete a purchase – the digital equivalent of a shop assistant lowering the price or making a special deal.

When customers use geo-fencing, then it is safe to assume that they are pretty serious about buying something. Once they scan the product, the sharp retailers will offer a special offer right away to capture that purchase.

Retail is changing considerably. Levi’s have implemented customer-generated outfitting, as have Heels. Customers can match tops and trousers for example, and then share the images with their friends via Facebook to get their opinions. And now the rise of price transparency could put an end to the closed environment of modern retailing.

These digital initiatives may take us back to the oldest markets – where rival retailers call out the prices, and always prepared when necessary to haggle!

So, you as the customer, will finally be King!