No foreseeable risks are anticipated for physicians. As for patients, one concern is that the exercise promotion messages, if taken without cautions, may to some degree increase the risk of heart attack for some patients. To eliminate this concern, the text messages suggest patients consult their doctors first before taking any exercise to reduce such risk to minimal. The risk of possible breach of confidentiality is addressed through using vigorous methods to protect the identity of subjects. After the data are collected, entered, and digitized, the investigators will store identifiable information in a separate data set and remove all such information from the main database (same to the information collected at the pre-intervention stage). The app will generate a unique identification number (ID) for each physician and patient for confidentiality use. Linkage will be through the study ID and performed only when necessary. Baseline and follow-up surveys will be linked by study ID only. As for the information collected on the app, they cannot be accessed without entering the password set by the physicians themselves. Only physicians, programmers and DKU research team members have access to it when necessary.