This armband is a relatively easy project for someone who can handle a sewing machine and it requires about an hour of your time.
Step 1: Things You Will Need
etc. sewing stuff
The most difficult item to come by will be the reflective band. It is definitely best to get something stretchy, and the easiest thing to make this reflective MP3 armband out of are Army PT armbands. I actually got the idea for this instructable a couple of years ago when I was in the military and had a bunch of these things laying around. They are required whenever soldiers do physical fitness, so I kept losing and replacing them, but would eventually find them again leaving me with a couple extras.
If you can find the armbands in a military surplus store or online, then you can skip most of this instructable - it really simplifies the process because the armband is already half made!
Step 2: Measure and Cut
1. Measure the circumference of your arm, keeping in mind the thickness of your work-out clothing. [Mine is 31cm]
2. Measure the width of the velcro. [2.5cm]
3. Measure the reflective band to equal the circumference of your arm plus 3Xthe width of the velcro. [38.5]
4. Fold the reflective band to make it twice the length and cut. [77cm]
5. Figure out how wide the band needs to be to wrap around three sides of your MP3 player, with 1/8-1/4in (1/2cm) overlapping both sides. It should also be long enough to wrap 3/4 around the length of your MP3 player.