Humminbird Smart Cast Wireless Sensor Link - $79.88

The wireless transducer can be stationed anywhere within a 100-foot radius of the receiving unit and boasts a wide 90 cone angle for complete coverage of the area below. The Remote Sonar Sensor uses an internal sonar transducer to collect the data that's wirelessly transferred to the display in real time. The 100-foot depth capability is perfect for most shallow to medium-depth lakes, rivers and reservoirs. Wet Switch technology maximizes the life of the user-replaceable AA batteries by automatically shutting the transducer off when not in the water. It boasts 400 hours of auto-shutoff battery life. - $79.88