An apparatus for remotely monitoring variables comprising: one or more independently powered remote monitoring devices having means for sensing variables coupled to a microprocessor for receiving and processing variable data and means for transmitting the variable data to a control device; a control device having a means for receiving variable data from the one or more remote monitoring devices, coupled to a microprocessor for processing variable data and means for transmitting data to the one or more remote monitoring devices; the one or more remote monitoring devices being momentarily activated at programmed intervals, wherein during activation, the one or more remote monitoring devices transmit a beacon signal to the control device and/or further transmits processed variable data from the and/or a previous activation period, the one or more remote monitoring devices resuming a sleep mode after such transmission(s) and at the end of the activation period, the activation period being extendible.