Pulse transit time (PTT) is a promising method to estimate blood pressure using a wearable device. In this work, we explore the measurement of PTT using two bio-impedance (Bio-Z) sensors placed on the wrist 7.5 cm apart such that they can be integrated into a wrist watch. In order to take into account the different factors affecting blood flow in the wrist, a regression model is used based on multiple features extracted from the first and second derivative of Bio-Z. The estimated PTT is compared with a reference PTT measured from ECG and PPG sensors. Experimental measurements are conducted on three subjects and exhibited an average correlation coefficient of 0.77 for the PTT estimated from wrist Bio-Z compared to the reference PTT.