Exercise is the cornerstone of cardiac rehabilitation for people with heart disease. However, many of those with heart disease do not undertake sufficient levels of exercise, and therefore do not realise the benefits, such as increased cardiovascular fitness, decreased weight and improved lipid profile. The proposed study aims to improve existing exercise based cardiac rehabilitation provision using a (m)-health delivery approach. One hundred and seventy participants will be allocated randomly to receive a package of exercise prescription and behavioural support strategies via mobile phone and internet (m-health) for 6 months or usual care (advice to be physically active and encouragement to join a cardiac club). Assessments at baseline and 6-months will compare physical fitness, exercise levels, and quality of life in the different groups. If effective, this approach has enormous potential to improve the delivery of cardiac rehabilitation and could be scaled up nationally and internationally.