This paper introduces the design and implementation of non-invasive, continuous time, cuff-less, blood pressure (BP) system based on pulse transmission time delay (PTT). The wearable BP device processing and monitoring both are performed using Smartphone. The PPG sensor and the integrated ECG sensor are wireless connected to smartphone. An adaptive threshold peak detection algorithm is proposed and tested to enhance the measurement accuracy. The proposed BP system achieves a systolic BP (SBP):- 1.36±7.51 mmHg and diastolic BP (DBP):- 2.44±3.49 mmHg. A new 4-LED PPG sensor is also introduced which can save 30% power consumption and reduce the interference of motion artifact (MA).