How I Stopped Worrying and Learned to Love Eberron
This invention of House Sivis has revolutionized communication throughout Khorvaire. The speaking stone is a careful arrangement of dragonshard and arcane implements, designed to amplify a simple sending spell. A user has to be trained by the house in its use, making it almost useless for the untrained. The range is usually determined by the size and quality of the dragonshards implanted in the device, so when a smaller stone is used, it relays information to larger, central speaking stones before the information is sent to its final destination.
Although the device was designed to channel arcane energy, some psionically incline Sivis heirs have been able to use the stones for information. The caveat is that the sender and receiver must both be using psionic energy for the message to be sent.