A thermal imaging camera can show you where heat is escaping, so you can make choices about what steps to take in order to insulate your home.
This camera connects with an Iphone. You will need to download the Seek Thermal App.
It comes with a little case & a manual.
Features: 206 x 156 Thermal Sensor, 36° Field of View, 1,000 ft Distance, -40°C to 330 °C range, works day & night, waterproof case
Watch a guide on how to use it: https://www.youtube.com/watch?v=AlH3yYkCqE0