Unless you have the sensor/IP camera tied directly to your HG script, you will have a delay. The delay will depend on the method used, but I have found that the quickest way to trigger a motion sensor is to have it hooked up the the RPi GPIO directly. X10 RF is fairly quick, but it isn't 100% received (which is why it sends several times). If it misses the transmit, you will have to stand still for a few seconds and then move again for the module to send the motion signal again. If the IP camera is cloud based, the time it takes for upload to the cloud and then notify HG may be a few seconds too. If it notifies HG directly, it will probably be fairly quick so long as the code in HG is set up correctly.