BuyDig via Rakuten offers the Nest Temperature Sensor 3-Pack for $99. Coupon code "HOME20" cuts that to $79.20. With free shipping, that's the lowest price we could find by $19. They work with a Nest thermostat (not included) within a 50-foot distance. Note: This coupon can only be redeemed once per account. (You'll need to be logged in for it to work.)