I needed a way to carry my mobile phone for those times when I had no pockets or bag. My daughter was also constantly mislaying her phone, so I came up with this phone cosy.
My 2nd daughter also uses this to carry money at discos.

Double drawstring top so phone/money is kept safely inside.
Hope you find this as useful as I have.

Gauge is not very important as the cable ribbing is very stretchy and you work until length required.

The drawstring is made using a small crochet hook and a single chain stitch. This gives a strong thin cord, that is constructed very quickly. Alternatively you could knit a cord.
Yarn is held double throughout to get a 4 ply weight.