I use this in my longarm to prevent backlash and it works great. (Backlash happens when you are quickly changing direction, the bobbin wants to keep spinning even though the machine has paused for a second, and you get a 'glob' of thread on the back of the quilt.) The trick is to put a tiny bit of oil in the bobbin case before you put the Bobbin Genie in. (I usually just wipe the back of the Genie along the neck of the oil bottle to get a small deposit of oil.) As long as I keep my Genie 'oiled' I don't have the backlash, if it gets dry, then the backlash starts again.
Not sure how these would work in a domestic sewing machine.