Heater helps to increase phone temperature and serves as a hand warmer app. 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 to warm up phone
2. put your cold hands on phone
3. and just wait... (hot hands are ready ;) enjoy heater

Heater app is completely free