With the Google Custom Search iOS SDK by Google, users have access to the JSON API considering development in Apple devices. References include example applications, source, and service folder. AdSense, Calendar, and Cloud Storage are additional Google APIs that benefit from this library
As far as web search tools go, few have generated as much hype as Wolfram Alpha. The service, which bills itself as a "computational knowledge engine," differs from search engines such as Google, in that it does not return lists of web pages. Rather, Wolfram Alpha attempts to calculate answers to user queries. For example, a query of "los angeles county median household income" will return the result "$43,518."