I have used this product. i works really well in even over cast weather. it was a fairly bright day but still… works in the UK 

http://www.sustainablesource.co.uk

I want one asap, looks nice and small and easy to lug around.

I was going to point out that it is not really "green" just because it is renewable. Todays solar panels require vast ammounts of energy producing. It doesn't make up for not charging your cell with coal. Anyway, I think it must last longer than 20 years. Solar panels last 20-30 years, no? I think they're just afraid of going bankrupt by 2 years.

While this looks like a great idea in principle, I question it's true environmental impact.

How much energy goes into making it in the first place, waste chemicals etc. And how much energy is required to safely recycle it?

Economically viable? 

They quote a lifespan of 2 years on their webpage, If you used it every day for 2 years to charge your phone would you really save £29.99 over conventional mains phone charging?