Yes, you can permanently power the sensor using a USB wall adapter or external battery pack (both available separately). 

$   Please note that due to the heat generated whilst charging, WiFi devices with an internal temperature sensor will show a temperature a few degrees above what they should be indicating.                Once fully charged, this heat generation ceases and the sensor will eventually indicate the correct temperature and continued connection of the charger or external battery pack will have no            effect..  This anomaly does not apply to external temperature probes.