Is there a control out there for purchase which offers predictive text functionality similar to Outlook's autocomplete feature when e-mailing?

To me, this is a non-web feature and my gut reaction is no even if it was available it would be horrible. But a client wants this functionality so I am just making sure its not out there for purchase.

I came across this: http://www.codeproject.com/aspnet/combobox.asp which wraps functionality from http://www.deadbeef.com/index.php/dhtml_combobox in a webcontrol. Its a dropdownlist with autocomplete, but not really predictive text like Outlook.

I posted this in ASP.NET but this kind of functionality seems right up the AJAX alley (or drain... it sounds more like a drain cleaner ). Has anyone seen anything done like this on the web?