Mobile Elastic Strap
Elastic strap with loops to hold your mobile phone and pens all together.

Solution

The strap will keep all your necessities together when going for a meeting, class or break in the park. Use it with your favorite book, sketch book or notepad.
The elastic strap could be sold as part of the bigger package of yourfone.de notepad and pen. The pages inside could carry on the doodle theme by pre-printed yourfone.de images to encourage more doodling.