Looking at Google Chrome features that could be ported to Firefox with an add-on, one of the most obvious additions many people wanted to see was Google Chrome’s Omnibar.  It mixes both the search box and address bar into one browser feature. 

The simply named Omnibar extension gets the job done, and adds a few new features where Google let us down in Chrome.  First, the most obvious feature (as pictured above) it gives you all the features of the search box in your address bar.  The problem, and thing they can not duplicate yet – is showing search results in the Omnibar for Firefox.

Omnibar does support  searching multiple search engines for same query in one go.  All you need to do is use this type of setup:

A general search query is:
@engine1,engine2 your search query

or,if you prefer to give engine name at the end:
your search query@engine1,engine2

Might not be perfect yet, but it does show a lot of promise.  If you have suggestions for it, check out this thread about it, and if you want to give Omnibar a shot – download it on the Firefox Add-ons web site.