Sometimes the small things are the best. CardNinja is a simple yet effective "wallet replacement" - or more of a card pocket really - that can stick on the back of most smartphones or cases.

We know you're probably already thinking that your cards will fall out, but CardNinja has a sensei-like grip that can hold in one card or a whole bunch. We not only held it upside down, we positively jiggled it around to see if a lone Visa would go flying. But it didn't.

The adhesive pocket won't stick on to rubber-like surfaces, so some cases and the odd phone won't be compatible, but most will. Once it's on it's solid too. We gave it a good tug to try to peel it away from the phone case, but it stayed put.

We can see a lot of practical use for the CardNinja: Subway or Oyster cards needn't go missing again; bulging wallets needn't be seen protruding from back pockets; or when you've got those dancing shoes on it offers a practical way to cut down on what you're carrying.

Available in black, grey or purple, the CardNinja smartphone wallet costs $20. International shipping is available direct from the CardNinja website as there's no current distribution outside of the USA. - PAY MONTHLY PHONES Get the brand new Samsung Galaxy S9 and S9+ on the network that gives you 4G in more places than any other. EE runs the UK’s biggest and fastest mobile network, offering superfast 4G in more places than any other operator after pioneering the UK’s first superfast 4G mobile service in October 2012. The networks coverage extends to 90% of the UK’s landmass and EE has received extensive independent recognition, including being ranked the UK’s best overall network by RootMetrics.