In Danny's blog post about the new Google Suggest beta he mentions a similar type of query refinement tool available from AOL's new Pinpoint Shopping.
It's also worth mentioning that Surfwax has offered a dynamic query refinement tool called "LookAhead" for almost a year. It's available with their news search database and offers search-terms based on a controlled vocabulary.
Optimising Digital Marketing Campaigns with Search, Social and Analytics
At SES London (9-11 Feb) you'll get an overview of the latest tools, tips, and tactics in Paid, Owned, Earned, Integrated Media and Business Intelligence to streamline your marketing campaigns in 2015. Register by 31 October to take advantage of Early Bird Rates.