This recent article, Bionic hand is gripping stuff (From thisisoxfordshire), talks about the use of a device called the SaeboFlex. It is a hand brace with springs that stretch open a clenched hand and allow the wearer to exercise weak muscles that otherwise cannot be moved. People who have suffered a stroke or spinal cord injury can potentially use this treatment to regain function in their hands.

I first learned of the Saeboflex while inpatient for physical rehabilitation after a spinal cord injury. The device was new at the time, and unfortunately I haven't had access to one myself. However, a friend who makes leather armor created a similar device that I have been using. After just a few days of resistance exercises with the glove, I have seen improvement in my ability to open my clenched hand. I'll add more updates and photos of the device in the near future.