Very handy app for anyone who uses national rail as part of their commute. And it often gives you a heads-up of the platform you need before the information goes on the station departure boards, which can often save you a battle at the gates.
Photo app for making images in the style of 1950s advertisements. Some of the pre-designed stamps are limited and it would be nice to have some more vintage fonts to use, but the app is a lot of fun to mess around with.
If Alan Turing had an iPhone, things would be very different. I don't think he would've got a signal, but he would've been able to carry around a full collection of German Enigma machines.
This app lets you play around with the famous code machines and get an idea for how they worked.