Jeff makes Jensen wear a chastity belt to keep the other guys off him while they're on a very important trip together somewhere. Equal parts protection for Jen's ass & keeping what's his, see, in a place where he's not free to be as aggressively possessive as he'd like.

This means Jensen wouldn't be able to use the bathroom, to bathe, or jerk off unless Jeff permitted it...*beams happily*

Thinking it over, it could obviously work for an established relationship; it could also be the catalyst for them *getting* involved, what with the protective/possessive/permission issues.