1. A method of cufflessly and non-invasively measuring wrist blood pressure in association with a communication device, the method comprising: (a) detecting an electrocardiogram (ECG) and pulse wave signals from a wrist region of a user using an ECG sensor and a pressure sensor; (b) detecting feature points from the ECG and pulse wave signals detected from the user; (c) extracting variables for calculating a highest blood pressure and a lowest blood pressure by applying the feature points detected in step (b) to a blood pressure calculation algorithm; and (d) calculating the highest blood pressure and the lowest blood pressure of the user by deducing a scatter diagram using the extracted variables.