While many mhealth programs and digital technologies (interactive digital technology, iDT) are now widely available and at least some have been shown to help individuals monitor and improve lifestyle behaviors and improve clinical outcomes relevant to chronic disease management, it is still unclear how iDT can be rigorously optimized to engage large numbers of users in purposeful prevention and/or routine chronic disease management. Critical steps for population-level impact include: (1) optimizing the user experience to significantly increase the long term impact and widespread use of iDT; (2) data linkage, interoperability of platforms and systems integration to enhance their utility and scalability; (3) producing frameworks, guidelines and business models to enable widespread uptake and adoption of safe and effective iDT by consumers, health practitioners and health services. We have been involved with a series of 5 randomized trials published in the last 15 years that have demonstrated high levels of engagement with telehealth and voice-delivered programs as well as effectiveness in terms of clinical, behavioral, quality of life and economic outcomes. (1) The Logan Healthy Living program evaluated a phone-delivered physical activity and dietary behaviour intervention for primary care patients with type 2 diabetes or hypertension. (2) The ProActive Heart Program evaluated a phone-delivered secondary prevention intervention for myocardial infarction patients. (3) The MoodCare Program evaluated a phone-delivered coaching intervention for ACS patients with depression. (4) The TLC Diabetes Program evaluated an automated, interactive telephone intervention to improve type 2 diabetes management. (5) Most recently, the My Diabetes Coach Program has evaluated a mhealth program involving “conversation” with an embodied conversational agent to improve type 2 diabetes management. Good levels of engagement and improved health outcomes and cost effectiveness are comparable between our trials of humandelivered telehealth (Trials 1-3) and automated conversational delivery (Trials 4-5). Recently available smart voice assistants at home or on people’s mobile devices can now be used to help people with a variety of chronic conditions with information, guidance and coaching. The advent of this new technology provides tremendous potential to deliver conversational programs at scale with good reach, engagement, effectiveness and cost-effectiveness.