Searching Custom Fields

Hi,
I want to add a search form to my website that will search specific custom fields on pages. The websites is a travel guide that includes accommodation information. I want my users to be able to search the custom fields on my accommodation pages so that they can find suitable accommodation. My custom fields are Location, Budget and Rating.

Ideally the search will produce a search results pages ordered by relevance that lists each of the pages by title.

Does anyone know of a plugin or example of another WordPress website doing something similar?

Thanks,

Dai Bee