Meet the personal trainer to the stars -- Grace Lazenby talks about the way she's changing celebrity fitness

Personal trainer to hot chicks Grace Lazenby (she’s sculpted the likes of Brittany Daniel and Nikki Reed) jumps on the MP3 player bandwagon with iTrain, a downloadable exercise program for all you kids who’ve found those Tae-Bo videos too bulky to cart around. For as little as 99 cents (the same price as that Kelly Clarkson single you just bought!), Lazenby and her chipper staff will talk you through everything from cycling to ballet. ”iTrain is great, especially when I’m on the road,” says comedian Sarah Silverman, another Lazenby client (and, with her slim physique, a very persuasive spokesperson). We like this concept — especially the ”hip-hop yoga” program geared to teens — but we fear the day when some freak sitting next to us on a plane starts aerobicizing. Please, ladies: Save it for the hotel.