I do the heel cord stretch too, and I use a piece of equipment called the ProStretch to do it (ha, I had to get it to see what it's called, because it's known only as "the blue thing" around here). The therapist I had when I was around 8 ordered it for me. My mom stole it from me, though.

You can find it online. I stretch the achilles tendon with a latex resistance band. Sometimes, in my pool, I kick my legs as I hold on to the side. I love aquatic therapy. Before I left for college, I asked my therapist how I could stretch my hamstrings by myself, and she said to put the leg I want to stretch on a chair while standing on the other leg.
When I go the gym, I use the treadmill (just for walking).