Meet the BACKBULL: a piece of bodyweight training equipment that helps you build strength in your body without putting unnecessary strain on your lower-back. You can use it with pull up bars, smith machines, and power racks to give your body a tough workout. The below video shows the BACKBULL in action:
The BACKBULL engages your core muscles and does not put unnecessary stress on your lower back when performing rowing type exercises. Sets you back under $80.