Under Amour offers its Under Amour Armour39 Performance Monitor in Black for $99.99. Coupon code "MMFA39" cuts it to $30. With free shipping, that's tied with our November mention as the lowest total price we've seen. (It's also a current price low by $70.) The included chest strap fits chest sizes from 27" to 52". The module tracks your heart rate, calories burned, real-time intensity, and connects to your iOS or Android phones via several app options.