Catching fish is a serious business that often requires a ton of technology, but for the individual, that might be too much; a perfect alternative is the Realsonar Fishfinder. It is an ultrasound device that connects to smartphones via Bluetooth in order to show fishermen where all the fish are.
The Realsonar Fishfinder looks and floats like a buoy. It is meant to chucked into the water like a buoy as well. By doing so, it allows people to see up to a depth of 150 feet. Working at about 4 frames per second, this gives the user enough time to cast their line in the direction of the most fish before they decide to disperse.