Search suggestions are one of the most important features people like to include on their sites as it minimizes the chances of typo errors and facilitate easy search my providing relevant suggestions in real time. I use a similar search suggestion tool on my personal dashboard page which works exactly like the Google suggest page. I thought of expanding it to include suggestions from multiple search engines so if I want to search some product on Amazon or some knowledge article on Wikipedia, it would get suggestions from all the engines at once. Here you can find an easy way to incorporate multiple search suggestions on your pages using jQuery and a small PHP script which combines the search suggestions.
Demo and Download: http://lab.abhinayrathore.com/autocomplete/
Search suggestion engines it can support out of the box are: Google, Bing, Yahoo, Wikipedia, Amazon and Ebay.
For adding more suggestion engines, you can read the Configuration Options section on the page above. You can download the PHP script to combine multiple search suggestions from the link above.