A method of activating a tool can include displacing a device in the tool, the device transmitting energy to a receiver of the tool, thereby activating the tool, and the transmitting including a control circuitry increasing electrical current flow between an electrical power source and a transmitter in response to a sensor detecting a predetermined stimulus downhole. A system can include a tool including a receiver and an electrical load, and a device which displaces relative to the tool, the device including a transmitter, a sensor and an electrical power source. Another method can include displacing a device in a tubular string including multiple downhole tools, each including a receiver and an electrical load, and the device including a transmitter and a sensor. The transmitter transmits energy to at least one of the receivers in response to sensor detection of a predetermined number of the tools traversed by the device.