Well, Bing actually does that: if you open a search page in your browser and type "cali" it provides the suggestions for searches starting with that word. This is done from javascript code runnng in your browser and sending Ajax queries to the server. Since
this is happening inside your browser, you can always reverse-engineer the page (after all, your browser has downloaded all the source code) to see how it is done. You can also capture the http packets being sent from your broser to determine how it is forming
the requests to the server in order to obtain that information, and the kind of responses that it is receiving. However, before attempting this reverse engineering, I would suggest that you check out the available documentation, since it is very likely that
the APIs for performing these searches are already documented.
But anyway, the Training and Certification forum is not the best place to discuss this topic. I would suggest one of the development forums on MSDN:
http://social.msdn.microsoft.com/Forums/en-US/categories