I saw one demonstrated at the Amateur Astronomy Centre, Todmorden. Visitors were able to take pictures of the moon easily through their 16″ Meade – Thanks to Peter Drew who invited me over.
I use a Baader Microstage II. I don’t have anything to compare it with, but it is well made and easy to use. The ‘clickstop’ function, which enables you to swing the camera out of the line of the eyepiece without removing the entire holder, works well.
You need to attach a simple smartphone holder which can be easily obtained.