GPS is short for Global Positioning System. This is a worldwide system of satellites that allows for calculating your location when outdoors.
IPS is short of Indoor Positioning System. Instead of satellites, this system is able of calculating your location through the use of nearby Wi-Fi or Bluetooth devices. There is no need for you or the X-Guard team to be logged in to any of these devices. The IPS system is accurate enough to calculate your exact location within a building, and can therefore send your required assistance immediately to the right apartment on the right floor.