This small gemstone which comfortably fits in the palm of your hand appears to mundane observation to be nothing more than a simple piece of jewelry. To someone attuned to the ether, however, it is a tool that allows its user to focus their powers. When you take ownership of this stone, or pass on its ownership to another, it will attune the user to the ether if they were not already and allow them to use the stone. (Transfer of ownership is a contractual process and it cannot be forcefully taken nor can the user be coerced into a transfer.)
A blinker stone functions like an etheric lens, allowing the user to focus their thoughs and draw forth their etheric power. A beginner will be able to generate minor effects like illusions of fire or other elemental phenomena, produce small lights, and so on. Through training, it is possible to produce a wide array of supernatural effects but the road to mastery is long and arduous.
If the user focuses their thoughts on their stone, they are able to project themselves into the ether to perceive its location and observe the stone's surroundings. Other beings attuned to the ether will be able to sense your presence as will you theirs. At will, and regardless of the distance, the user can summon their blinker stone back to their hand.
(A blinker stone is traditionally a gift between romantic partners. If you gift this blinker stone to anyone, they will become aware of this fact once they accept ownership.)