Try it out at Metabot.GG Aim Trainer. It will track your accuracy and reaction speed, and give you feedback on what to focus on. Your stats will be compared against other users that have used the aim trainer and show you how you compare on your end stats screen. Based on your data and how it compares to other users, it will give you tips on where you can focus for improvement.

This tool is brand new, so comparison stats need to populate a bit as people play it. Average stats for the game are weapon/difficulty dependent, so the comparisons you see will be dependent on what you selected.

I'll work to improve and enhance it over time, I just want some initial feedback (and requests if you have any). This is something I can continue to grow if there is interest in an easy-to-use web based tool like this. I make these types of things for fun on my own time.