In 2004 Green Roof Technology was probably the first in the United States specifying Leak Detection systems in combination with Green Roofs. Actually, the most reliable system on the NA market came also from Germany where these have been proven over decades.
If your are planning on putting up a new roof and or green roof, be sure to consider getting a waterproofing membrane that is compatible with an electric field vector mapping system (EFVM). This beauty can be installed before or after a new waterproofing is assembled and can find leaks that wont show up in a traditional flood test. A leak may be in one section of the house however, the water may travel several feet before coming through the ceiling and playing a nice tune in your pets water bowl. Having one of these systems prevents you from turning your roof into swiss cheese or a patchwork quilt trying to find and fix that illusive leak. This also saves your green roof from total annihilation by knowing exactly what area to dig up.
In the long run this saves time and money and is cheaper than sketchy waterproofing membrane warranties.