The Iridium communication satellites have a peculiar shape with three polished door-sized antennas 120° apart and at 40° angles with the main bus.

Occasionally an antenna reflects sunlight directly down at Earth creating a predictable and quickly moving illuminated spot on the surface below of about 10 km diameter. To an observer this looks like a bright flash or flare in the sky with a duration of a few seconds.

This app displays in real-time where is each Iridium satellite predicts when these flares will occur from the observer's position and allows from the 3D locator locate the exact point in the night sky.

Gets the data needed from android device (accelerometer compass location) and from the following urls:
www.celestrak.com and www.heavens-above.com