I've actually done that with a tens unit and some creative workmanship. Keep it low for arousal and general fucking. Turn it up when I'm ready to blow or flood a cervix or asshole.
Fabulous - remind me: is pre-cum just seminal fluid with no sperm in it? like when a bloke with a vasectomy cums? is that device available on AliExpress? my Mistress would love one to control her sub