However, it's annoying when it's 6 am and my mp3 player lands in a pool of goo.
This instructable is my solution.
My design is based on the Puuko friction sheath.
The iPod slides in, but it doesn't go out.
Step 1: Materials and Methods
(1) piece of scrap leather
(1 yard) proper cordage [dental floss (Free, since I'm a dentist.)]
leather hole punch
Step 2: Layout
Make sure it fits right. Leather is skin. Just like plastic surgery, each piece of leather has different tension lines. Try folding your leather in different ways to find what works best for your configuration.
2. Lay out the seams.
You'll want to have some play. I personally added in 3-4 mm of tolerance to prevent the leather from ripping. Also, you should taper the seam to allow some space around the mouth, so that iPod slides in easier. Mark your seam line with a pencil.
3. Lay out slots for the straps.
The slot should be slightly wider than the armband to allow for movement.
Step 3: Cut slot
This results in a cleaner, less prone to tearing slot.
2. Cut the slot between the holes.
I used my scissors for this, but you can just as easily use a scalpel or an x-acto knife.
3. (Optional) Smooth out the slot.
You may have made a perfect slot, but I didn't. I just went back with my scissors and smoothed out the slot to let the strap have smoother action. Plus, it just plain looks better.