It doesnt look homemade at all. The thing is not all in the same plane, the small ring/hook is at 90 degrees to the rest of the article.
I did wonder if it was some kind of cable holder, as used to keep front brake cables from rubbing against mudguards, but there is no obvious place to mount it apart from drilling a hole in the mudguard and I sure that if BMW intended it to be mounted in this way then they would have supplied the mudguard with a hole already in it.
Les