It always sucks to buy something in a store, come home, and realize that it was available online or at another store for $50 less. You bonehead. Way to do your research.
Well, a service called Frucall will allow you to be impulsive yet still protect yourself from overpaying. Simply call the toll-free number (1-888-DO-FRUCALL), punch in the barcode number from the product you're planning on buying, and it'll give you the cheapest prices at which it's available. Soon the service will start allowing text messages and mobile Web price checking, but it doesn't get much easier than calling. So go ahead, go to Best Buy with no prior knowledge of how much you should spend. It's still not the brightest way to shop, but at least now you're somewhat protected.
Note: Adam Frucci is in no way related to the Frucall company or any of its subsidiaries.