Concepts are a funny phenomenon.

Car manufacturers use them to make us swoon, and then they remove all the cool bits and send yet another horrible hatchback to the showroom.

Mobile phone concepts can be like that too - but while some of the coolest mobile concepts probably won't end up in your pocket any time soon, the technology they show off just might.

So what's coming down the phone pipe?

Here are our five favourites...

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Greenheart1. Sony Ericsson Greenheart

It might not be as exciting as other firms' designs, but Sony Ericsson's Greenheart concept is likely to have a big impact.

In environmental terms mobile phones are as warm and cuddly as Hitler, so SE's boffins are trying to make phones as green as possible.

Greenheart uses bio-plastic housings, recycled plastic keypads and environmentally friendly packaging.

The firm is currently showing Greenheart to "selected partners in the industry" to identify which features should reach mainstream phones first.

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Packet2. Emir Rifat's Packet

Let's get the obvious joke out of the way: most men would be delighted if their packet won a prestigious award.

But Packet is no laughing matter: this fantastically foldable mobile phone concept won first place at Instanbul Design Week 2007 and no doubt ensured that industrial design student Rifat won't be short of job offers.

Like most concepts we doubt we'll ever see this one in the real world, but it's a great bit of design nevertheless.

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Morph3. Nokia Morph

There's more chance of John Sergeant joining Girls Aloud than there is of Nokia's Morph coming to a Carphone Warehouse near you, but as an example of gee-whiz we've-drank-lots-of-cider thinking it's hard to beat.

In the far future, Nokia reckons, phones will get their power from the Sun, clean themselves, use integrated sensors to find out about the world around them and bend into new and interesting shapes. Bet they still cut out halfway through important calls, though.

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T3 014. T3 01

After years of reviewing less than perfect mobiles, the gadget fiends at T3 decided it was time for action - so they asked their readers what they wanted from a mobile and teamed up with design gurus The Alloy to come up with a concept.

Now in its second incarnation, the 01 takes the best ideas from across the mobile market and sticks them into a single, rather sleek device. Build it! Build it now!

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Samsung5. Samsung folding OLED phone

Samsung showed off this concept design at Japan's FPD International 2008 technology conference.

While it's a good few years from production the prototype proves that bendy mobiles are definitely on the horizon.

Imagine an iPhone that folds in half and you get the idea - much better than the grainy YouTube grab you see on the left.