Apple is hoping that Apple Pay, a tap-to-pay service integrated into the iPhone 6 and Apple Watch, will help it dominate the $79.2 billion-a-year digital payments market. But can Apple succeed where so many have failed before, and truly replace our wallets with our phones?

With 2 million users, a deal with Starbucks, and $6 billion worth of transactions, Square is turning smartphones into checkouts, digitising loyalty schemes and reshaping how consumers spend – without using NFC technology.

With the release of Apple's iOS 8 in September 2014, Touch ID - the fingerprint sensor functionality on iPhone 5 and 6 - is coming to the forefront. As well as adding an extra layer of security, some brands are seeing the sensor as an opportunity to enhance m-commerce.

While most people pay for goods online in their native currency, as mobile payment systems mature - boosted by Apple Pay - and new currencies flourish, soon digital wallets may have a new job: helping pick the best currency for each transaction.