This is my Kinsa – got tired of never having a working thermometer  No batteries; plug it into your phone and it keeps a log of temperature readings.  It’s really cool!
By using your smartphone, Kinsa takes advantage of 25,000X the processing power of a regular digital thermometer – virtually no electronics inside and no batteries required – so the thermometer is extremely lightweight and durable for carrying  and always ready to use.  Now pay only $14.99 with free shipping.  It’s $18.99 on Amazon.