Wired's Nicole Martinelli looks at the RFID Wellness Smartkey from Technogym. The key measures your current level of fitness, then designs a customized exercise program based on the results.

After the initial test, Martinelli says, "My next session began politely enough. I inserted the three-inch plastic key into a color monitor in the weight room. 'Welcome NICOLE MARTINELLI, take a 5-minute ride on the stationary bike,' it instructed."

And after the bike ride, the key suggested a series of exercises on weight machines. "At each machine, it noted bench height, weight, number of reps and the length of the timed breaks I should take after each exercise," Martinelli writes. "If I couldn't remember how to use a particular machine, I could just go back to main monitor for a video clip."

The system's more than two million users, Martinelli says, include the Italian soccer team AC Milan.