I’m a big fan of the MantisX system. I’ve been using it since the original model came out years ago. The newest handgun iteration (they make an AR-compatible system, too) is small and discreet enough to mount on the bottom of a pistol magazine. If you stop and think about that placement, you’ll realize it’s now compatible with a holster. In the original iteration, you mounted the Mantis device on the pistol rail, which was fine for shooting, but ruled out using the system for holster-oriented practice. The company even makes a variety of replacement magazine base pads with an attachment point for the MantisX. If your pistol isn’t included in that offering, no worries; there’s a universal mount offering, too.
Let’s jump ahead to why all this really matters. The motion detectors in the X10 version of the device, combined with some nifty software enhancements for the companion smartphone app, now analyze your draw in exquisite detail. By breaking down the complete draw sequence into five discrete steps and timing each with every draw, you can figure out where your technique is smooth and efficient and where you need work.