Sometime in the weeks following New Year’s the novelty of winter begins to wear off. The once-invigorating brisk chill in the air just makes us want to head back to bed.

LAS VEGAS — Selling big-screen TVs and entertainment systems to couch potatoes has been the bread and butter of the consumer electronics industry for years. Now, a host of upstart companies want to serve a helping of vegetables to those consumers in the form of health-and-fitness gadgets.