Latest fitting for those of us whose guitars sport a locking nut- Tone Vise Keyless lock. It's aimed at addressing the hassle of carrying nut wrenches to lock/ unlock the nut.
- looks totally unattractive
- subject to a wide embrace by the industry, spares for worn out/ lost parts remain limited
- if you are into locking nuts, you won't mind the separate wrench application to begin with
PIC: Tone Vise youtube