I had a really bad case of chronic tendonitis (not carpal tunnel syndrome) for about 3 years without any relief. I had inflamed tendon pain throughout both my wrists and arms all the time and I was getting ready to quit my job because of it (I am a programmer).
This device does a really good job of building arm strength but did not help my tendonitis all that much. I think something like this may have been helpful at preventing my tendonitis, but by the time I started using it my arms were so bad that no amount of strengthening/stretching would help because ultimately my tendons needed to heal.
Thankfully, I found a therapy that did a great job of helping my wrist/arm tendons heal and I haven't had problems with tendonitis for a couple years now. For anyone struggling with wrist/arm tendonitis, I HIGHLY suggest you do the following at least once a day until your tendonitis is gone:
Get around 10 pounds of ice from a gas station and put it in a bucket wide enough that you can fit both of your forearms comfortably in the bucket (I used a plastic foot bath bucket). Fill the bucket with water so that the ice moves around freely and it is easy for you to completely submerge both of your forearms in the bucket. Now that you have the ice bucket ready, fully submerge both arms in the ice water for between 10 to 20 seconds. Continue to do this every 10 minutes for about an hour.
I often did this for up to 2 hours, usually while watching tv or something. All in all it took about 6 months of doing this everyday before I was tendonitis free (though my arms felt much better after just a couple weeks), but it was well worth it, as I was getting ready to change professions.
I found this therapy from a book I bought from this site: www.tendonitisexpert.com
As the site explains, the above therapy addresses a vicious cycle of inflammation that prevents healthy blood flow to the tendons. By forcing blood in and out of the affected areas with ice the cycle is disrupted, your tendons slowly start to heal. Definitely give it a try, it changed my life!