A free program for Android, by Ninjetic Studios.

Real Ghost Tools is an app that combines a visual radar with a word detection system. With this, you can have a complete ghost hunting kit in your pocket. It works best with GPS-enabled devices. If you are using a device that does not have GPS, you can set the location manually. This is to allow for true north detection. It will work best with the device in your hand.

Each dot is colored to represent the strength of a single entity seen on the radar. If a detection goes outside of radar range, then that same detection returns within the range of the radar. You will notice the same color, or if it is different, you will see a unique color. Each color is graded on the strength of the signal from any one radar blip across ROYGBIV color spectrum.