There’s a short summary of a project called ‘Mobile Heart Health’ in the latest issue of IEEE Pervasive Computing (April-June 2009).  The project was conducted at Intel Labs and uses an ambulatory ECG sensor to connect to a mobile telephone.  The ECG monitors heart rate variability; if high stress is detected, the user is prompted by the phone to run through a number of relaxation therapies (controlled breathing) to provide ‘just-in-time’ stress management.  It’s an interesting project, both in conceptual terms (I imagine pervasive monitoring and stress management would be particularly useful for cardiac outpatients) and in terms of interface design (how to alert the stressed user to their stressed state without making them even more stressed).  Here’s a link to the magazine which includes a downloadable pdf of the article.