Source: http://lifehacker.com/5559238/priceblink-is-a-real+time-background-price-comparison-tool
Chrome/Firefox: If you're looking for a price-comparison engine that integrates with your browsing experience but have been put off by some of the privacy issues surrounding popular price-comparison add-ons, you might want to take a look at lightweight and privacy conscious PriceBlink.
PriceBlink integrates with Chrome and Firefox and idles in the background waiting for you to do some shopping. When you visit shopping sites PriceBlink offers seamless suggestions, showing you were the products are cheaper at other retailers.
Where PriceBlink stands apart is factoring in shipping charges. You won't have to visit a site where a product is $5 cheaper just to find out that shipping actually makes it $3 more than the site you're currently on. PriceBlink also keeps an eye on coupon and deal sites to make sure you never miss coupons and free shipping codes. Check out the video above for a walk through or visit the links below to install it for Chrome or Firefox. Have a favorite price-comparison extensions or site? Let's hear about it in the comments.