This thermometer from TempTraq will monitor your child's temperature for up to 24 hours. The thermometer is a skin patch containing a printed battery and a Bluetooth transmitter and antenna that sends temperature data to your phone up to feet away. When the device goes out of range, the free app, available for IOS and Android, notifies you of that fact.
The app will also alert you if the your child's temperature hits a set monitoring point. It's capable of monitoring multiple children and stores temperature histories for the entire monitoring period.
The patch is made of a non-latex material, is water-resistant, and both physically secure and easy to remove.