You cannot manually record your temperature. The reason for this is that with a normal thermometer you always measure the wake-up temperature and not the actual basal body temperature. The basal body temperature is the lowest temperature your body reaches while you are asleep. 

The wake-up temperature comes close to this temperature, but it is not precise enough. trackle determines the actual basal body temperature and therefore recording the wake-up temperature would "falsify" the curve.

In addition, according to the rules of the symptothermal method, only the same thermometer may be used within a cycle in order to avoid measurement deviations.