Physical Education The most accurate fitness tracker E very January, millions of people resolve to get more exercise. Health-club memberships spike as does interest in fitness trackers, which use accelerometers to record activity. The trouble with those devices, though, is that they rely on binary tracking algorithms—moving or not—so they generally can't tell the difference between a steady jog and vacuuming the living room. The Amiigo is the first tracker that can discriminate between exercises, tally reps, and accurately tabulate calories burned. The device consists of a shoe clip and a Bluetooth-enabled bracelet, each with a three-axis accelerometer, microcontroller, battery, and enough flash memory to store up to five days' worth of data; the band also contains an infrared blood-oxygen and pulse sensor. When the wearer opens the Amiigo smartphone app, it prompts the bracelet to transmit its data. Algorithms process that data to determine what kind of exercises the wearer has done (barbell curls versus hammer curls, for example) and how much of each one. The Amiigo recognizes more than 100 exercises, but the company plans to release app updates to include more—from sit-ups to bat swings to Frisbee tosses. EDITED BY Corinne IOZZiO WHATSNEW@POPSCI.COM STORY BY Corinne Iozzio BATTERY LIFE Up to 2 days PRICE $119 (est.) AVAILABLE Spring PHOTOGRAPH BY Sam Kaplan EFTA00558019