Via its official blog, Wolfram Alpha just announced its Anrdroid app, named Wolfram Alpha for new T-Mobile G2 with Google and it's available now in Android market for only $1.99 lot cheaper than when the same app was firstly registered in Apple store, it was $50, but then reduced to $1.99.
With Wolfram Alpha app you will have the access to its huge data repository plus ten trillion data elements. All of them to be used to answer your questions. In other words it is search engine based on computational. Unlike the general search engine which displays the whole documents into a list on result page, Wolfram Alpha answers factual queries directly by computing the answer from structured data, for example if you are stuck with math problem, you can send it to this app, it will return you with the correct answer. One more thing you would like about this app is there a feature to do keyword search via voice.