Buydig has Garmin Striker Cast with GPS, Castable Sonar, Display Fish on Smartphone or Tablet for $139.99 (22% off list of $179.99). Not into fishing myself, but thought this was an interesting product. Reviews on Amazon seems not bad. This went on sale recently for $149.99, but $139.99 is the lowest I have seen based on my research.
Amazon also has this at $139.99
- Wirelessly stream sonar, locate fish and display them on your smartphone or tablet
- Built-in GPS lets you create your own custom fishing maps
- Quick, easy out-of-the-box setup
- Performs well in shallow and deep water