This Kinsa Smart Thermometer drops from $19.99 to $14.99 right now at Kinsa. Plus, shipping is free. This ties with the best price we've seen so far this year and is a current price low by $5 (compare here and here). This thermometer works with both Apple and Android devices, and when paired with their free app, you can take highly accurate temperature readings in about 10 seconds. It requires no batteries and uses the headphone jack. Sales tax is not charged in most states.