Meet the Swing-OPS Speedsensor: a smart swing measurement system that accurately measures your bat speed, swing power, and tightness. You will be able to access the data on your smartphone. The display gives you quick access to bat speed after each swing. This Bluetooth enabled speed sensor can record 50 swings in the standalone mode.
The Speedsensor attaches to any bat using an adjustable strap. It lets you see your swing path and acceleration during each swing. You can get yours for under $100 at this time.[where to get it]