Sixty-four patients scheduled for a total hip arthroplasty via a posterolateral approach were randomized to receive conventional mechanical alignment guided acetabular component positioning with smartphone-assistance to function as a pelvic tilt goniometer to assess pelvic motion (n=32), or sole conventional mechanical alignment guided acetabular component positioning (n=32). The primary outcome of interest was the incidence of cup placement outside of the Lewinnek safe zone. Secondary outcomes of interest included radiographic measurements of inclination and anteversion angle, deviation from target inclination (40deg) and anteversion (20deg), and the incidence of adverse events. Radiographic assessments were performed 6 weeks post-operation. Study results revealed a statistically significantly lower incidence of safe zone outliers in the smartphone group compared to the conventional group (p=0.008). No statistical differences in inclination angle (p=0.567), anteversion angle (p=0.856), deviation from 40deg inclination (p=0.494), deviation from 20deg anteversion (p=0.643), or incidence of posterior dislocation (p=1.0) were observed between the two groups. Operative time was 14 minutes longer in the smartphone group, however the difference was not statistically significantly different (p=0.069).