The comparison-shopping space gets another player with the beta launch of Pronto.com, a search engine featuring 50,000 merchants selling 45 million products.

Pronto.com will use patent-pending technology to crawl the web for product listings to be listed alongside paid results, much like Google does with sponsored links that appear atop generic search queries, ClickZ reports. The company is also offering a downloadable browser tool, called Pronto Shopping Messenger, that allows users to receive real-time messages about products they are viewing on websites.

The tool is available for Internet Explorer and as a Firefox extension, and can trigger instant alert notifications about price drops and alternative product selections available across the Web.

In the long-term, Pronto.com wants to use the power of IAC's network of high-traffic sites, including Ask.com, Match.com and Lending Tree, to make the site the starting point for product searches.