The purpose of this research study is to see if a lottery which provides the opportunity to win money, a reminder system using a "Med-eMonitor", or the combination of both might be useful in helping patients to achieve better control of their anticoagulation therapy. Selection for the arms of the study is randomized by the study computer. Some will participate in the daily lottery only, some with the reminder system only, some with the reminder system and the daily lottery, and some with neither the lottery nor the reminder system.