Google has announced a small but powerful update to its mobile product search engine - blue dots which indicate stock status in stores near you. However, it's limited to certain - US-only - retailers, including Best Buy, Sears, Williams-Sonoma, Pottery Barn, or West Elm.

The way it works is pretty simple. When you search for a product, it'll also look for your location and cross-reference the data with the inventory databases of various nearby retailers. If there's a match, then you'll be notified with a shiny blue dot. Clicking that will bring up the nearby retailers that have the product you're after, and you can see their address, phone number, and get directions.

It could prove useful if you find yourself in desperate need of a gadget on the move. However, until it hooks into the inventory systems of far more stores, it could end up being more of a novelty than a useful tool. Happily, Google's got a web form for retailers to sign up - so if you're interested in being a part of the project, you can.