I swear by back on track, whether it's the blanket for their back muscles or the boots for their tendons. I feel like that sort of heat/ceramic - therapy is wonderful and without it my horses suspensories wouldn't have recovered as quickly. And, my baby horse is much happier when her back is warm.
Back on Track is awesome because of the ceramic fibres in the products, so they can actually stay on a touch longer than a magnetic blanket (4 hours max the first time, generally increasing with each use)
My horse spends a little time every day in a fancy magnetic/massage blanket (owned by the barn I manage). He sits through a 30 minute cycle...20 minutes with the magnets, 10 with the massage (sometimes I'll give him a few extra minutes of the massage if I get busy doing something else). It helps him warm up his muscles and relax.
I love Veredus magnetic boots. They take the swelling right out of my mare who stocks up very easily. They have a dri-tex liner which is removable which is nice because then you only have to wash the liner, not the actual magnetic boot as frequently.