Abstract: Wearable coin-sized sensory devices, and related systems and methods, providing immediate wireless notification of activities occurring on separate electronic devices, such that the invention can be worn in contact or near contact with the user's skin, which does not require the user to replace, reconfigure or retrofit items already possessed by the user and worn on the body, and which does not disturb others in the vicinity of the user. When one of the designated separate electronic devices not actually held in the user's hand or face-to-face with the user, e.g., emits a wireless signal as a result of an occurrence on such separate electronic device, the invention senses such wireless signal and immediately produces a tactile indication, silent or near-silent, to the user. The invention is merely coin-sized and thus can be versatility attached or affixed to items in contact or near contact with the user's body in multiple ways.