Weatherproof, Wireless and mains power free Building site security alarms. Monitor and protect any building site with a GSM building site alarm that will call and text your security guards, staff or police when an intruder or burglar has been detected on the building site. The external PIR movement detectors provided are fully weatherproof and ready for outdoor use. The movement sensors are battery powered. GSM wireless building sites alarm systems for outdoor site security with external PIR movement detectors idea for remote monitoring.