I recently started running in the mornings.
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

Materials:
(1) piece of scrap leather
(1) armband
(1 yard) proper cordage [dental floss (Free, since I'm a dentist.)]

Tools:
leather hole punch
heavy scissors
(optional) needle
pencil

Step 2: Layout

1. First, try laying out the leather around your iPod (or other mp3 player).
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

1. Punch holes at the ends of the planned strap 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.}

Step 4: Punch Holes

Punch holes along the seam that you marked earlier.
_{Helpful details:

1. Having about 5 mm between each hole allows for a clean looking stitch, enough material to hold the seam, and close enough stitches to control the tension of the joint.

2. Allow enough space from the bottom stitch to the bottom of the leather to allow flex. I have a junction of about 15 mm, which allows the leather to flex around the ipod.

3. I find that laying the leather in the final drape and punching through to the other side results in a very nice, lined up seam.}

Step 5: Stitch Up

Stitch up the holes that you've made.
You can use any cordage that you want to.

_{Personally, I used dental floss.

I'm a dentist, so that it's available.

It's also cheap, tough (it's nylon), and waterproof.

I like to start the seam with a surgeon's knot.

Be sure to have equal tension with each stitch.}

Step 6: Enjoy

Finally, thread in the strap and enjoy!

The ipod should easily slide in, but will be tricky to slide out.
The leather shapes itself as the ipod enters.
Those ancient Scandanavians really knew what they were doing.

For more dental related stuff, please check out my blog.