Here is a smart sensor that you can use for barbell tracking and velocity-based training. The MoveFactorX Barbell Sensor weighs 25 grams and takes only 8cm of space on the bar, so it won’t get in your way. It captures your movement and gives you feedback on your power, force, speed, and bar distance.
This MFX barbell runs on a coin cell battery. It has a LED indicator to let you know when it is in standby mode. You can find out more about it here.