Founded by serial-entrepreneur Dan Wagner and with nearly $100 million in funding behind it, London-based Powa has long been promising to to revolutionise in-store, mobile and even television commerce.

After several delays, the firm has now finally unveiled its hybrid technology PowaTag 'concept', which chiefly comprises a mobile app which stores users' payment details.

Like Barclays Buyit, the PowaTag app will let shoppers buy products by snapping QR codes in print adverts, whether in magazines, on billboards or price tags in stores. Goods are then shipped to their homes.

The firm says that it is also tapping the audio and visual sensors in smartphones to let users buy straight from television, YouTube and radio adverts.

Meanwhile, Bluetooth Low Energy technology - recently embraced by Apple and PayPal - will be used to ping customer phones with product information and offers as they wander around stores. The BLE beacons will also let stores collect data on participating customers' shopping habits.

Says Wagner: "Retailers can no longer afford to think in terms of online verses offline - they must seriously rethink how they connect in-store and online strategies to provide the agility and innovation needed to enable customers to buy whenever and wherever they may be, when they are at that critical buying-decision moment."

Powa charges 25 pence, or 0.1% of the sale value, per transaction. So far 240 firms around the world, including Universal Music and Carrefour, have signed up. Several charities, which are being offered PowaTag for free, are also onboard.

Stephen Partridge, director, e-commerce, Universal, says: "PowaTag will transform the way fans access and purchase music and merchandise from their favourite artists, both online and in the real world. We are excited by PowaTag's instant purchase capabilities and the potential it has to open up additional revenue streams for up and coming and established artists."