Weights:

Smaller and larger weights, dangling from your nipples or your balls, or perhaps even from your cock.

I'll keep adding a little more weight, simply because I wish it. Simply because you're willing to do this for me, because you don't want to disappoint me, or because you're too stubborn to use your safe word.

Weights that dangle directly from your skin, but also weights that can be attached to the ceiling with eye bolts and rope, for example, so they'll dangle a bit further away to become a threat and a part of the session.