A smartphone holder you can mount on the X axis belt tensioner to monitor your printing process. It is made out of 2 parts, so you can design your own thing. 

For this type, you will need 3 10X5mm neodimium magnets and some electrical (rubber)tape. The tape is required to increase the adhesion of the smartphone to the printer.

Changes on the V2 version:

• shorter arms
• inversed holes for the screws. The nut should now be below
• included fusion360 files in case you need to adapt it for yours.

Screw and nut: M4, 45mm and DIN557 GB39 M4 

https://www.aliexpress.com/item/4000075591731.html?spm=a2g0s.9042311.0.0.27424c4dmNbeOq

https://www.aliexpress.com/item/32875607040.html?spm=a2g0s.9042311.0.0.27424c4dmNbeOq