Just do it. One of the most successful marketing slogans of all time, the phrase conjures up images of young titans in Lycra running, jumping, hitting, kicking and splashing their way through life, all with a strange tick shape on their shoes.

Yet look for the champions of tomorrow and, we are told, they prefer to Just Sit, eat crisps and play video games. Especially the video games. The average school pupil fiddles with them for two hours every day and scientists have blamed this for the explosion in childhood obesity. Increased "screen-based entertainment" was highlighted as a pitfall of modern British childhood in a headline-grabbing letter signed by more than 100 experts last week.

Nike, however, thinks it has the answer. The US sportswear giant has invented an electronic gizmo that sits in the shoes of video-game players and rewards their exercise in the real world with prizes in the virtual one. The company's "game pod" would measure distance run, walked, hiked or cycled and transmit this information to a video game, to trigger extra playing time, hidden levels or special features.

Nike has filed a patent on the invention, which it calls "a system for promoting physical activity for video game players". The technology relies on a pedometer, pressure sensors or GPS tracking to record the amount of exercise, and a detachable memory chip to plug into the game console. Slackers and those tempted to cheat by driving their shoes round the block a few times should beware - the patent says the game pod chip could be configured to measure increased heart rate or even blood oxygen content instead.

In a neat twist on survival of the fittest, sweaty activity could be rewarded with on-screen changes to a user's video game character, with extra "virtual strength, endurance or speed" on offer. And games could be made impossible to play until the chip registers a specified level of activity.

Nike previously teamed up with Sony to develop EyeToy: Kinetic, a video game that uses cameras to capture exercise routines on screen, but would not comment if it was working with games manufacturers on the game pod or, indeed, when it might be launched. Rumours that key staff were unavailable as they were jogging round the car park to earn sufficient credit to log on to their computers could not be confirmed.