Wolfram|Alpha has released an iPhone and iPod Touch App. At $50, it's certainly one of the more pricier apps available in the App Store.
Mashable says the app has value as a graphing calculator, stock analyzer, etc. But as CNET points out, you still need a web connection to get the info and it's free to simply point your mobile Safari browser to WolframAlpha.com. CNET does admit the app is more optimized visually for the iPhone. So basically, you're shelling out $50 for a mobile version of Wolfram Alpha.
If you work a lot with numbers, it's probably worth shelling out the $50, though I would wait to see if the price comes down a bit. If you've forgotten everything you learned in your freshman calculus class, you probably don't need this app.
Here are the official screenshots from Wolfram|Alpha:
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