Matt Egan has been looking for one device to rule them all. He hasn't found it.

Convergence is good, we are told. And sometimes that is the case. The best tool is often not the best tool, it's the tool you have when you need to use it. It's why your smartphone camera probably gets more use than your DSLR. The high-end snapper takes better photos, but during the moments you need to capture it is more likely that you will have your smartphone in your pocket. And typing out an email on your phone may not be the most fun you can have, but I bet you send a lot of email from your iPhone or Android.

Good smartphones are good enough to replace both your compact camera for photos and your laptop for email. But it doesn't necessarily follow that one device can or should be your tool for everything.

Of course that may not matter in a world full of the internet of things. If every device from your fridge to your tablet top to your TV is connected to the web, will you ever need to find the best tool for a single task? I think that you will, as I prefer to use certain devices only for certain tasks (although 'need' might be a strong word in this case).

Two tools good, four tools better

Possibly I am a crank, but when I was recently on holiday I found that although my iPad is a great eReader, an e-ink device such as an Amazon Kindle would have been so much better. Why? In part because reading on a backlit screen is no fun at all in direct sunlight, and also because I had only one plug adaptor and having to charge up my book each night was a pain. The Kindle would have been better, although the iPad was perfectly fine.

Traveling home from the airport I used a standalone satnav device. Either my smartphone or my wife's would have worked, but they have smaller screens, less accurate GPS and batteries that just love to drain quickly. The satnav is good for only one thing, but good it is.

Reader, I even recently bought an iPod classic purely on which to play my favourite music. I commute every day and I like music. I don't always have web connectivity to stream music, and my smartphone and tablet quickly fill up so I don't always have the song I want when I want it. The iPod is perfect for the task in hand. Portable and robust with great battery life, and not even half full even though it has more than 20 years of music purchases stinking it out.

I may be in a minority, but I suspect not. (See also: Twitter - not news.)

Post-PC world, post iPad

Take the change in messaging around Apple's iPad tablet. iPads haven't proven to be the one device to rule them all - and this despite Apple's early messaging being around the iPad being a 'new category of device' leading us to a 'post-PC world'. It just hasn't happened. Don't get me wrong, the iPad family are great, market-making and -changing devices. Apple changed the world with the iPad. But as great and fun as they are, they are principally consumption and communication devices. Laptops and PCs are going nowhere, and even Apple now talks about the right tool for the right task, particularly when launching new MacBook laptops.

Indeed, there is no small irony when you look at the relative lack of success of Microsoft's Surface Pro, the response to the iPad. The Surface Pro is a tablet that is also a perfecty servicable laptop and with a screen and keyboard could make a great desktop PC. But it is perfect at none of these things and that, in part, is why Surface Pro is struggling to make an impact. You could avoid the Surface Pro, buy a laptop and a Nexus 7, and still have a tonne of cash left over from what you would have spent.

It's not that Surface Pro is bad. Far from it - it's a magnificent device. I just don't think that level of convergence is required.

Smartwatch, dumb idea

You can see it elsewhere - smartwatches aren't yet popular. Perhaps Apple will be able to change that, but in the meantime single use activity trackers and runers' GPS devices are popular. Even more so in the US. They do one thing very well. And that's better and cheaper than shelling out for a smartwatch that does everything poorly.

It's possible I am wrong. Stranger things have happened and it's not as though I saw the iPhone, the Kindle or the iPad coming down the tracks. But I suspect that convergence is related to convenience and can go only so far. And the great single-use device is here to stay.

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