We have developed a tele-rehabilitation application for training cardiac patients. It uses a modified ergometer bicycle with a set of wireless sensors. While the patient is exercising, the ECG, blood pressure and oxygen-saturation are monitored constantly and automatically. If sensor values exceed pre-defined thresholds, the patient receives an alarm. As a result the training will either be stopped or continued at a reduced load, depending on the severity of the alarm. To measure user acceptance, we introduced the system to 13 members of staff and four patients, who trained on the system every day during their stay in hospital. A total of 39 training sessions were completed. In 27% of the exercise sessions an ECG connection could not be established and in 23%, blood pressure measurement failed. However, there were no failures to measure oxygen saturation. The overall acceptance of the patient's graphical user interface (GUI) was excellent. The doctor's GUI with its functions received an overall score of 1.5 on a scale of 1 to 4 (usefulness 1.6, usability 1.3 and operability 1.6). The SAPHIRE tele-rehabilitation system operated properly and was well accepted by patients and doctors.