Although I've been in the creative business for 22 years, I actually trained as a physicist. And I still have a soft one for all things maths and the like. So when I discovered this app, I nearly died and went to calculatory heaven.

The i41CX+ iPhone, iPod and iPad app.

The webiste is atrocious, but the app is ace (and at £14.99 with the printer module, which you need, that is a big ace, this is not a 59p thing that is okay but throwaway, this is serious)

http://alsoftiphone.com/i41CXplus/

It is a simulator of the CLASSIC (and I mean classically revolutionary) Hewlett Packard 41CX calculator launched in 1979. When I went to university I wanted one, but couldn't afford it, it was about £300 in 1984, more than a car. It was available until 1990 and people actually collect them and everything.

It comes with a set of retro and modern skins and works like a dream. Proof that design is more than aesthetic. Design is what something does.

If you aren't maths-savvy you might find it actually hard to use as a calculator, but if you have even half a maths brain get it, you'll never use the in-built Calc app ever again.

But just look in the window of our office, you'll soon work out that I like 80s stuff.