Mark Bridge writes:

What would you say to a tiny little device that enabled you to recharge your smartphone almost anywhere, whenever you wanted?

This is pretty much what a US-based company called Nomad is promising. In fact, they sent me two of their latest products to try.

But first, a quick look back at my personal mobile phone history. My Nokia 2110 delivered around 30 hours of standby time. The first Nokia smartphone - the 9000 Communicator - achieved something similar. An Ericsson r380 from 2000 (running dear old Symbian) managed something like 120 hours. Last year's HTC One, which is my current handset, has a 2300mAh battery delivering up to 500 hours of standby. But that's theory. Today, in real terms, it barely manages a day of average use. Don't blame the phone; blame the apps.

As a result, I've developed a strategy. If I'm going to be out for a while, I carry a spare battery with me. Well, technically it's a UTOO 'power bank' with a built-in micro USB cable, but it's just a clever battery as far as I'm concerned. Of course, I need to make sure the power pack is always charged for whenever I need it - which can be a problem if I'm out for a couple of days in a row.

So I carry a spare mains charger as well. This isn't as much of a challenge as it sounds: I have a folding Mu-brand plug and a USB cable. That plug is a beautiful piece of design; it's like a baby Transformer. As a result, the combination of plug and cable is almost pocket-sized. It would be genuinely pocket-sized if I didn't already have a battery in my pocket.

And so my heart skipped a beat when Nomad got in touch. Could I say 'goodbye' to my collection of accessories? A couple of days later, a cardboard envelope dropped through the letterbox.

Inside were two devices, each in packaging that's only a few millimetres thick. Here we go...

I started with the Nomad ChargeCard. It's a microUSB cable in the shape of a credit card (8.1cm by 4.6cm by 3mm). Let me explain. On one corner of the card - which reminded me of some 'keyless' car keys - is a microUSB plug. Clipped into the centre of the card is a USB plug; one of those 'skeleton' plugs that has four gold teeth but no outer shell. You unclip the USB plug, which has a short flexible cable attached, and you're now able to charge your phone wherever there's a USB socket. Your PC, a friend's laptop, a game console, in the car... plenty of choices.

The theory is great, although my combination of HTC One and old Dell XPS laptop didn't work particularly well. I couldn't charge the phone 'face up' without worrying that the orientation of the sockets on my laptop and phone could cause the card to act as a lever and break something. A longer cable would have helped - but that would also result in a less pocket-friendly product. Despite this, it’s still a remarkably tough and flexible product. I may just be a worrier.

I also felt the designers had missed a couple of tricks. Firstly, a hole in the corner would let you use the card as a key fob - or add it to your keyring. Yes, I know it's designed for pockets and wallets but what's wrong with multi-tasking? And on the subject of wallets, is there any chance future versions could have a little cap for the microUSB plug? Okay, I might lose it after a few days but it would stop me from worrying about the protruding plug damaging something.

On to the Nomad ChargeKey. It's an even simpler design than the ChargeCard; a short (6.6mm end-to-end) flexible cable with a skeleton USB plug on one end, a microUSB plug on the other and a keyring loop near the microUSB plug. Add it to your keys and then forget it... until you need it, anyway. Has it made a hole in my trouser pocket? No. Have I needed to take care of it in any special way? No. Has it broken? No. Will it be staying on my keyring for the foreseeable future? Absolutely. I can even charge my phone from my laptop without removing the rest of the keys.

Although I've been testing the microUSB versions of Nomad's products, there are also versions that offer a Lightning connector for anyone with an Apple iPhone 5, 5c or 5s, as well as compatible iPads. The company is selling its products online via its own website at hellonomad.com for $29 and also via Amazon for £20.

The Nomad ChargeKey and ChargeCard aren't a permanent solution to the problem of smartphone battery life. That's something for manufacturers to solve. But they are certainly a practical alternative to carrying a mains charger, cable and spare battery around all the time. Anyway, what kind of person would do that?