The purpose of this study is to find out whether it is feasible (acceptable to participants) to use a smartphone app to send text message reminders to take palbociclib, and whether these reminders are effective at helping people remember to take palbociclib according to the treatment schedule.

Inclusion Criteria:

• Patients with a breast cancer diagnosis who are initiating therapy on palbociclib (Ibrance)
• >/= 18 years of age
• Able to speak, read and write English
• Willingness and ability to send and receive text messages with intervention app
• Own a mobile telephone "smartphone" with text messaging capabilities. Only iPhone or Android operating systems support OhMD Application
• Criteria applicable for both Control and Intervention groups
• Flip-phones do not support OhMD Application and thus ineligible to participate
• Initiation palbociclib (Ibrance) for the first time, either as monotherapy or in conjunction with other medication such as Lstrozole (Femara) or Fulvestrant (Faslodex)

Exclusion Criteria:

• History of taking palbociclib (Ibrance)
• Patients whose caregivers coordinate their health care

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.