This simple Instructable describes protecting the iPhone power cord with shrink tubing.
Step 1: What You Are Trying to Prevent
The iPhone is a significant investment but the power cord is surprisingly vulnerable to kinks and tears. To protect against this I applied a two inch length of shrink tubing. This serves to reinforce the collar.
Step 2: Slip on the Tubing and Apply Heat to Shrink It
I use a heat gun but you can use a soldering iron or even just use a lighter to shrink the tubing. The tubing shrinks into place and holds fast.
Step 3: The Finished Project
You can see the finished product here again. I've found this much more durable.
The other advantage is that my cords are color coded so I can quickly find the right cord for each device.