Scrying stone

Scrying stones are devices that were created by the Highborne which can be used to communicate across distances. They appear to enable two-way visual and audio communication between whoever is using them.

Known
Known scrying stones are found in Azshara and Azsuna.

Related quests

 * Amberwind's Journal (quest)
 * Arcane De-Construction
 * Hacking the Construct

Speculation
What Varian Wrynn used to communicate with Captain Taylor could be a Scrying Stone. However it was a recording, so it didn't happen at that very moment in time.