A trial will be conducted on 200 breast cancer patients with adjuvant hormonal therapy. The study included 6 months baseline measurement, and 12 months intervention. Patients will be assigned to high adherence or low adherence group. Then, through randomization, low adherence patients will be assigned to the intervention or control group. Study Coordinator delivers the intervention using the WALKON mobile application. Control participants receive usual care with continuous monitoring using Medication Event Monitoring System (MEMS) device.