http://www.vivehypnosis.de/?p=5378
This will give you a trigger you can use to slowly make you dumb. Unlike “String of Dumbness” you won’t notice any effects when you put on your trigger, instead you will slowly grow dumber while you wear it. The whole process will take time, allowing you to incorporate the effect into other play or just enjoy slowly loosing your mental capacity. Once you take the trigger off, you will return to normal within 5 minutes. As a little extra it will be impossible to remove the trigger yourself if you have been triggered by someone else (you allowed to use the trigger).
You either need a length of string or a bracelet for this, and you need to war it while listening. This string or bracelet will be your dumb trigger whenever you wear it around your wrist.