WolframAlpha App for iOS
'Remember the Star Trek computer? It's finally happening--with Wolfram|Alpha. Building on 25 years of development led by Stephen Wolfram, Wolfram|Alpha has rapidly become the world's definitive source for instant expert knowledge and computation.
Across thousands of domains--with more continually added--Wolfram|Alpha uses its vast collection of algorithms and data to compute answers and generate reports for you.
Parts of Wolfram|Alpha are used in the Apple Siri Assistant; this app gives you access to the full power of the Wolfram|Alpha computational knowledge engine.'
This app costs $3.99