By putting a video screen where it's least likely to be ignored by shoppers, a company called MediaCart thinks it has discovered the key to in-store video advertising, reports Advertising Age.

The video screens pull RFID signals to display marketing messages to the person pushing the cart. Ads, according to research by the company, should ideally be no longer than a few seconds in order to not distract the shopper too greatly. The time during checkout might be the exception: One example might be for a Disney DVD that would attract the attention of kids on a shopping trip with parents.

Ad retention is high in the test scores, but some worry that number will will drop as it becomes just another ad medium ignored by the public. Measurement of the ads could be an asset to marketers, since ad viewing can be strongly tied to eventual purchasing. Pricing for the ads is likely to be on a CPM scale.

MediaCart is not the first player in the shopping-cart-as-ad-medium space, but it is the first to break out of solely regional testing. Its trials are running in the Northeast and in Texas. Procter & Gamble and General Mills are participating in the Texas trial, but MediaCart would not identify marketers in the Northeast test.