The only DSM that I know of that has a stitch regulator is one of the Bernina models. I believe it is computerized to interface with the machines on board computer.
On LA it is often computerized and senses how fast you are moving the machine and regulates how quickly the needle goes up and down to match your movement speed. It results in even stitches. I have one on my LA and have never quilted without it on. You can adjust them to how many stitches per inch you want.