This mod requires Baubles, and is only useful on a multiplayer server or LAN world. It won't do anything for you in single-player.
Friendship Bracelet is a replacement for server plugins that allow commands like /tpa to teleport to other players, done in a more engaging and fun manner. Instead of just typing in a command, you create a friendship bracelet out of string, an ender pearl, and dyes for coloring the strings . As soon as a bracelet is crafted, it binds itself to the player who crafted it (you can right click to bind it to yourself if the bracelet was made in an autocrafter).
Once your bracelet is bound, you can equip it as a ring bauble or give it to a friend. Whenever you're online and wearing your own bracelet, your friend can hold right click with their copy of your bracelet to teleport to you. Teleporting takes five seconds, then requires a fifteen-second recharge.
To carry many friendship bracelets without using inventory space, you can create a bracelet keyring. This can hold up to six bracelets, and holding right-click on it will let you teleport to the bracelet in the top slot. If you equip a keyring as a bauble, only people whose bracelets are in the keyring can teleport to you. Note that this will be overridden if you have your friendship bracelet equipped.