Free heater app helps to increase phone temperature and serves as a hand warmer. It also protects your battery from very cold temperatures.

The principle of heating app is computational task to increase cpu temperature and battery consumption and therefore phone temperature.
It is not a special work to produce heat from phone but a ordinary tasks which phone does very often.

The effective way to warm hands asap is:

1. Start the heater app
2. put your hands on phone (to cover it entirely)
3. and just wait... (hot hands is ready ;) enjoy heater that is actually warm)

Heater app is completely free