Kaiser Health News has a great article on the medicare penalty for hospitals that high readmission rates. Over 2000 hospitals in the nation (that is nearly 50% of all hospitals) will be penalized for $280MM in 2013. The penalty list includes some of the most well known hospitals in the nation. You can see the full list here.
Apparently, they are not doing enough to engage patients they discharge. There are several proven ways for hospitals to reduce readmission rates, but almost all of those approaches are human intensive (e.g., requiring nurses to call patients on a daily basis), and hence very expensive to implement. I believe that this area is ripe for technology disruption. After all, technology has replaced many human intensive call centers in other industries!