The use of mobile and web tools in health care has greatly improved interactions between doctors, patients and healthcare professionals in the past few years. According to the University of Texas Health Science Center at San Antonio (UTHSCSA) almost 75% of the 296,980 women in the United States that are diagnosed with breast cancer will have hormone receptor-positive breast cancers. Endocrine hormonal therapy (EHT) is very effective for nearly all women with hormone-receptive positive tumours and is the most widely prescribed one. The dedicated use and adherence to this therapy for 5 years has also shown larger reduction in recurrence [6]. However, even with such proven benefits, the adherence is limited to just 33% of all the women who are prescribed. In such cases, the use of interactive easy-to-use apps would promote and improve adherence [2]. Such apps should enable fast responses to patient queries, guide patients through treatment, help them understand symptoms, motivate them through educational content, and prompt interaction with their peers. In this paper, we describe an approach for accelerating app prototyping using the existing Google Android platform and converting it to a cross-platform web application thereafter. Google Firebase [1] is used as a database server to assist in monitoring and sending notifications to users without compromising the safety and security of patients' data. The proposed system and approach can also be further tailored for similar technology-assisted health promotion and intervention studies. The effectiveness of the approach is evaluated through a randomized controlled study with breast cancer patients conducted by the UTHSCSA research team.