InvisibleHand, if you weren't sure, is a Firefox plug-in that lets you know if the item you are shopping for can be found cheaper elsewhere by way of a handy link - enabling you to hop over to the other shop and buy the item.
Launched into beta back in August last year the plug-in works by trawling the Web to match the product you are looking at, if found cheaper it will send you the alert and link or alternatively let you know whether you are currently viewing the best price.
InvisibleHand has also released some stats, which reflects a pretty positive uptake since its launch, which includes 103,000 downloads on Firefox and now that there's a Chrome plug-in, 25,000 users on the Google browser. More relevant to anyone wanting to save a bit of cash, however, is the £6.5 million of savings it's found for UK users and $42.8 million for those in the US.
If you want to give it a try you can visit the InvisibleHand website here, and be sure to let us know what you think in the comments below.