The purpose of the study is to learn more about ways to help patients understand and manage side-effects from hormone therapy. The investigators will use the information from this study to design future studies to better understand how our well our tools work to help patients monitor and manage symptoms from hormone therapy and to stay on their hormone therapy for the recommended period of time.

Despite robust available data supporting the efficacy of oral endocrine therapy (ET) for the treatment of breast cancer and the low adherence to this life-saving treatment, only 6 randomized controlled trials have assessed interventions to improve adherence to ET; only 1 showed modest short-term benefit. ET adherence is critical, as 10-year survival decreases from 81% when adherent to 74% when non-adherent to ET. The investigators propose a first of its kind, randomized, culturally tailored mHealth intervention trial called "EmSHAPE"- Engaging mobile health for symptom monitoring and health promotion for endocrine therapy - among newly diagnosed women with early hormone receptor positive breast cancer. Prior intervention studies have not been effective.

Inclusion Criteria:

• Participants must identify as a woman
• Participants must be age 18 or older
• Participants must have a diagnosis of Stage 0, I, II, or III HR+ breast cancer
• Participants must have started initial treatment with standard of care oral endocrine therapy (ET) (i.e., tamoxifen, anastrozole, exemestane, or letrozole) within 16 weeks of study registration.
• Participants must have completed surgery for treatment of breast cancer at least 14 days prior to randomization.
• Participants who received chemotherapy must have finished it at least 14 days prior to randomization.
• Speak and read in English
• Own an internet-enabled cell phone
• Capable of using the electronic pill bottle
• Concomitant radiotherapy is allowed. Concomitant maintenance targeted or biologic therapy (e.g., anti-HER2 therapy, osteoclast inhibitor therapy, CDK 4/6 inhibitor, ovarian function suppression medications) is allowed.

Exclusion Criteria:

• Metastatic (Stage IV) breast cancer
• Male gender
• Prior treatment with endocrine therapy for breast cancer
• Communication difficulties such as: Uncorrected or uncompensated hearing and/or vision impairment, uncorrected or uncompensated speech defects, uncontrolled psychiatric/mental condition or severe physical, neurological or cognitive deficits rendering individual unable to understand study goals and tasks

Participants must identify as a woman.