The present invention provides a wearable device, comprising: a power source; a position sensor electrically connected to the power source, for sensing a position of a wearer of the wearable device and generating a position signal; a signal transceiver electrically connected to the power source, for receiving the position signal, sending the position signal to a monitoring apparatus, and receiving an indication signal from the monitoring apparatus; and a body of the wearable device comprises a first part and a second part, wherein a relative position of a moveable end of the first part and a moveable end of the second part can switch between a first relative position and a second relative position.