A multifunction electronic key is provided with at least one wireless communication interface that can function as an access control key to unlock an electronic lock when the key is placed in proximity of an electronic lock that has been previously configured to allow temporal access to the said electronic key, and at least one of the following functions: a) Measure the electric field experienced by the device, process it and optionally send it to a second wireless device; b) A physical button to communicate a distress signal to a second wireless device, in response to which the second wireless device estimates the position of the electronic key and generates a system alarm indicating the identity of the electronic key that generated the alarm and its position estimate; c) Measures the device's motion, process it and optionally send it to a second wireless device; d) One or two way audio communication via the wireless link; e) Measures ionizing radiation.
Method and system for planar, multi-function, multi-power sourced, long battery life radio communication appliance