I go to an adult massage place (no not a prostitute house). They offer these services at the end of ever session. I actually asked "Do you mean a hand job?" and it's really just like a massage therapist massaging your outer labia, inner labia, and pelvic area. They don't go inside your vagina or stimulate the clitoris. For males they do outer prostate massage around the pelvis, perineum, and they massage the penis and testicles.
I have never said yes to it. Not because I am in a relationship, but just because I find it very weird to have a stranger touching my kitty. My fiance and I do this as a couple though... quite often actually.