InvisibleHand Firefox Add-on Always Gets You the Lowest Price
Automatically shows a discreet notification when a better price is available on a product you’re browsing. Covers over 50 retailers in US and UK.
InvisibleHand shows a discreet notification when the product you’re browsing can be bought for a lower price elsewhere. It gives you a link directly to the product page at the competing retailer.
Web browser Add-on for Firefox 3.0 – 3.6+
Download: InvisibleHand 1.8