Phones in essence is a useful idea, but extravagant designs for a phone would take forever to program. Simple things like /msg would be great and a warp menu, but minigames would need to be a multiworld thing because minecraft itself can not handle using a gui to create a minigame. /msg and warp menus would be pretty easy to do, but a smartphone would be unstable to stay the least. The server already as a wave of lag every once in awhile so a phone would have to be pretty small. A phone working as a crafting gui would be interesting allowing the player to access slimefun machines, but installing a plugin that created a phone that would replace the need for slimefun crafters would be nightmarishly unstable and op. So a simple phone plugin would work, but creating a virtual iphone would be too unstable and op to implement.