Communication Stones

A magical device produced in the Elven Realm that allows communication over a distance.

Utility

Short range stones are often used by family members or friends to communicate throughout the day, such as asking someone to do some shopping on their way home or letting a spouse know you'll be late. 
Medium range stones are often used by those who travel frequently, such as merchants, diplomats, or nobility. They may be used to keep in touch with friends or family they are away from, or to keep abreast of current news in a particular area. 
Long range stones are often used similarly to medium range, just covering longer distances.

Manufacturing

The stones must but properly cut before they are enchanted, then specially polished to retain the enchantment. 
Enchantments take the form of lyrical speaking or even songs, with more verses needed to utlise more magicka.

Access & Availability

In the Elven Realm, it is fairly easy to get a hold of bracers for short range communication - such as those living in the same city or region. Longer range bracers are more costly, requiring more complex enchanments - and faster long-range bracers are even more costly. 
Outside of the Elven Realm, bracers are more rare for being luxury goods, but not significantly more expensive by comparison.

Complexity

While the bracers themselves do not need to be complex in construction - most being a message opal set as jewelry - the enchanments that go into longer range communication stones become increasingly complex.
Short range stones are often set as rings or earrings, as the enchantment can fit into the smaller stone. These stones cover a range of a few square miles, usually enough for a city or small collection of towns or villages.
Medium range communication stones are usually set as bracelets or neacklaces, needing a larger stone to house the enchantments. These stones cover a range of several hundred square miles, usually enough for a country.
Long range stones are usually set as bracers or mantels, needing still larger stones to house the necessary enchantments. These stones cover a huge distance, usually an entire realm with the possibility for inter-realm communication.
There are also two ways of directing messages - passive and active delivery.
Passive delivery allows the magical messages to traverse natural flows of magic without aid, naturally drawn to its paired stone or stones. This method can cause a delay of a few days for longer range stones, but this is still faster and -in the Elven Realm, cheaper - than most traditional methods of letter sending.
Active delivery encases the magical message in a second bit of magic which takes the message to its intended recipient directly, significantly cutting down on the time it takes to send such messages.
Interrealm delivery can be passive or active, but does require additional protective measures.

Discovery

Message opals are a natural stone found in the Elven Realm - two people holding a stone from the same area can send short-range telepathic messages to each other. It was later that coastal Sun and Forest elves started figuring out enchantments that refined the message sending capabilities.