This is a photo of my Kinsa – bought it last month ’cause I got tired of never having a working thermometer when needed – who keeps button batteries in a junk drawer, anyway?  With Kinsa there are no batteries; plug it into your phone and it takes and keeps a log.
By using your smartphone, Kinsa takes advantage of 25,000X the processing power of a regular digital thermometer – means there are virtually no electronics inside and no batteries required – so the thermometer is extremely lightweight and durable for carrying  and always ready to use.  Pay $19.99 with free shipping.

Was super easy to set up – it talks you through – we tested PITA:  NO FEVER.  There’s also a link to check out symptoms.  Screen looks like this.