If you want to monitor the rear of your estate, you can mount an outdoor IP camera and connect it to the Alarmhandler.
Indoor and outdoor IP cameras use the same technologies, either detecting differences in images or difference in the detected body heat. Outdoor cameras normally use PIR detection = body heat detection. This can be adjusted so the sensor does not to pick up eg. animals in the garden. PIR detectors are generally reliable, whether used inside or outside, as long as they are properly set up.
Use of IP cameras without PIR is also possible outdoors, but since most are intended for indoor use, you should mount them in a protective enclosure (eg glass dome) and adjust sensitivity such that shadows from the sun, etc. do not trigger detection.
