For more details see:
Alireza Sahami Shirazi, Diana Cheng, Oliver Kroell, Dagmar Kern, Albrecht Schmidt. CardioViz: Contextual Capture and Visualization for Long-term ECG Data. Adjunct Proceedings of Ubicomp 2007 (Demo).
Jonna Häkkilä, Anind Dey, Kari Hjelt, and I organized organized the Ubiwell workshop (Interaction with Ubiquitous Wellness and Healthcare Applications) at this years pervasive. Alireza presented another paper on heartbeat monitoring there:
Florian Alt, Alireza Sahami Shirazi, Albrecht Schmidt. Monitoring Heartbeat per Day to Motivate Increasing Physical Activity. UbiWell workshop@Ubicomp 2007.