Hi, sorry for my English..

I found this clip on passenger's mat.

 

Any ideas where came from? 

I don't see anything strange or out of its place

Possibly from the side panel of the dash board (The side you can see when the door is open).  Those shaped clips can be used to keep a plastic panel in place, and locate into a small oblong hole.

 

Gaz 

A pillar trims, in fact all the pillar trims, sill trims, rear side panel & tailgate trims, that clip is used on all of them.

 

Having removed a dashboard I dont recall any being used there or on the glovebox.

If you're lucky, something may start to rattle or come loose and then you can see if that clip should be holding that piece.

Has anyone fitted a dashcam, reversing camera, towbar or other powered accessories recently?

It's a pillar clip from the A Pillar.