It is a light green-colored device with a button, a red dial, and an antennae that are used to track sponges within a mile radius.
Role in the episode
Sandy invented it after SpongeBob went to New Kelp City. It was soon destroyed by Squidward as he did not want them to find SpongeBob. He destroyed it with a hammer, but claimed that he dropped it, when it was obvious he had not.