There are dozens of currency and unit converting app in the AppStore. Many of them are free – Convert is not.
However convert has a beautifully designed interface and well thought through interface, is easy to use and can convert a lot of different units that are grouped intuitively together.
I think in the case of this app, beauty and substance is worth spending a bit of money.
Unfortunately the app has not been updated for a while.
When I wrote this post, I was looking at version 1.0.1 for iPhone and iPod Touch. Requires iOS 2.1 or later. Available for 1,59 EURO / 1,99 Dollar in the AppStore.
Tried with iOS 4.0 and 4.1 on an iPhone 3GS.