Hermit Purple's vines are relatively weak, but they provide Joseph with considerable telepathic ability, enabling him to sense locations or thoughts by projecting them into a camera, or a TV, or even into an image made from the sand of a dusty street.
Joseph demonstrated that he can use the vines as a means of transporting himself between buildings, like a grappling hook or whip. This is used most as a way of keeping Joseph safe from dangerous situations, quickly pulling himself out of the way.
Psychic Photography: Apart from combat purposes, this versatile Stand can perform remarkable feats. It can produce psychic photographs by destroying a camera or another object. The photo will reveal the intended target as it is in that moment of time to show were the person is located. It also can produce live psychic videos on a television that will show the intended person and allows communication as well. The Stand can make the TV quickly change channels in a way to create an audible message of what Joseph wants to know. Hermit Purple also allows its user to read minds, but only with the use of a TV. It can also conjure real-time maps capable of tracking moving subjects, even being able to make a map out of dust on an unpaved road.
Hamon Transmission: Joseph has shown the ability to transmit Hamon through Hermit Purple as an extension of his body. Wrapping himself in Hermit Purple in such a manner was able to prevent DIO from touching him.
Along with activating his own Stand The World, it was stated that DIO's semi-precognitive abilities that seemed to have resulted from a Hermit Purple-like Stand were due to a Stand power that awoke in the body of Joseph's grandfather Jonathan Joestar.[1] Similar to Hermit Purple, it can produce a psychic photograph by striking a camera. (Although the camera is notably not destroyed, unlike Joseph's usage, implying it to be a more efficient version of Joseph's Hermit Purple) DIO used this technique to track the Joestars and their friends' current location to send Stand Users after them. This Stand is also capable of showing an image present in someone's heart through a crystal ball. DIO used it to show Polnareff one image of J. Geil, as that image represented the pain Polnareff felt in his heart. The fact that this version of Hermit Purple manifested within Jonathan's Body could possibly explain why Joseph has Hermit Purple as well.
(The italicized information below derives from a Light Novel not written by Araki. As such, it may or may not be considered canon.)
In contrast, in the JoJo novel, Jorge Joestar, the stand is given the name, The Passion and has the ability to view the past and future of the user's blood relatives (including a relative in another universe).
Trivia
Hermit Purple is one of two Stands wielded by a Joestar that does not have a humanoid appearance, the other being his daughter's Stand.
Hermit Purple is also the only Stand wielded by a main JoJo without a humanoid appearance.
Hatate Himekaidou's psychic photography ability from Touhou Project functions in the same way as Joseph Joestar's Hermit Purple; Hatate even wears purple clothes.
Hermit Purple's thorns can briefly be seen in the background of the second opening of the JoJo TV anime, "Bloody Stream". This acts as foreshadowing, as the episodes that the second opening is attached to adapt Battle Tendency, and Joseph does not develop Hermit Purple until the following part, Stardust Crusaders.
Gallery
Joseph and the Tarot card representing The Hermit
Joseph's Hermit Purple "taking" a spirit photo
HermitPurpleEffect2.jpg
Joseph's Hermit Purple used on a TV
DIO's Hermit Purple used on camera
Joseph's Hermit Purple projecting what's on Joseph's brain onto a TV
A map of Varanasi made with Joseph's Hermit Purple's ability
Joseph's Hermit Purple used on a plane
Hermit Purple seen in the second opening of the anime's Battle Tendency saga
