Well, I have two different "sticky pads" at home. The bigger one can barely hold my iBasso D10 and my Cowon D3 together, but due to the fact that the back of the Cowon is kind of a matte surface it is not that good.
Then there is the "sticky pad" that I have in my car. This one holds anything like it is mold in concrete.
I do not know how the principle work...
The one that holds things vertically is the one you recommended in that eBay link?