We need a band to install the sensor in it, so we are going to make a band.
1. Cut felt, 240X70mm size, and fold with short sides to make a band.
2. Stitch long side except 50mm hole in the middle of it, so after that it can install a sensor in.
3. Stitch short sides
4. Sew velcro to attach the band.
5. To put some Rhinestones using fabric glue on the band as much as you want(option)
If you are not familiar with this you can see the illustration instruction
Here is a making band template