This is the Mantis X8: an app connected motion tracking system that helps you take your archery game to the next level. It stream data to the MantisX app on your smartphone and tablet. The sensor tracks every movement of the bow before to after your shots. It gives you feedback on your aim and shot stability.
The Mantis X8 lets you view each phase of your shot against others to see how well you are performing. It identifies patterns in your shooting and tracks your performance over time. The Mantis X8 is compatible with 99% of bows, including longbow, compound, and recurve bows.[where to get it] [official site]