Sendstone

Made from smoothly carved rock & enchanted.
While holding it you can choose a name on the
stone and cast Sending. Sendstones are connected
by putting them in contact for 1 minute, then
saying a name aloud that appears carved in the
stone. Each can be connected to up to 3 others,
if another is linked a name of your choice is lost.
If no creature bears the named stone, you know
as soon as you attempt. Once Sending is cast
with a stone, it can't be used until the next day.