I've fixed both Achilles tendonitis and plantar faciatis (from running) with massage. The plantar facia is easier to reach, but even with the Achilles I've fixed it in one very painful session. I use a hard plastic massager thing and rub it against the tendon, doing as much of it as I can reach. I keep my hand on the other side so the tendon can't move. Eventually all that lumpiness goes away and it quits hurting to rub it. A pair of pliers with ice-insert jaws would be perfect, to give better leverage for squeezing the tendon and rubbing it. As far as I know that tool doesn't exist.

I'm not kidding about how painful this is, but it works. I do stretch quite a bit, heel drops off curbs or putting the ball of my foot up against a pole and stretching that way. I also hunker (heels on the ground) rather than sit on the ground or bend over to do something at ground level. I cut back my running to no more than 2 days per week (15 miles or so) and bike more for cardio. So far no injuries at all from bicycling though when I trained for my triathlon on a borrowed road bike with clip-less pedals that made my feet hurt. I just have platform pedals on my bikes.