Sentinel is an earthquake measurement service in New Zealand providing measured shaking data from the Sentinel sensor network. This data is used for resilience planning and to guide building occupancy decisions. For users of the free App, Sentinel sends you colourised maps of measured ground shaking. For a chosen location or interest or a "Friends & Family" location. With a paid subscription to the Sentinel service, the Sentinel App also sends your building status to your phone and tells you what to do: carry on business as usual, visually inspect for hazards, or evacuate and seek expert advice.