The Military Grade Portable Smartphone Fishfinding Sonar from FishHunter is so small, you can almost carry it in your pocket. It’s shrunk down to fit inside a 8.5″ X 6.2″ X 3.0″ red rubber ball. It has a rechargeable battery inside, and it comes with a charging stand. You just float the military-grade sonar transducer in the water, and you’ll see all the fish swimming through its cone-shaped listening field on your smartphone’s screen. The transducer connects to the smartphone, either Android or iPhone, via Bluetooth. You’ll get maximum information from a minimal package. It’s $179 at FishHunter.