Long time listener, first time caller

I have been looking to do more rope bondage and as part of that I've been researching how to do it safely. One thing that was mentioned in the demos I've watched and other materials I've consumed is that when the sub/bottom is prevented from speaking there needs to be a means of giving a distress/stop and get me out of this signal. A common suggestion is having them hold something that can be released if they need to give the signal. That all makes a lot of sense and I've got a couple items that could be used for that. However, my concern is that in the heat of the moment it may take too long to notice it has been dropped, particularly if this is happening on a softer surface like a bed, carpet or blankets, which might not make much noise if something were to fall on it.

My question is, does anyone have a suggestion for something that is easily held in the hand but will emit noise and/or light when it is released? Suggestions for other methods are also welcome.