Yes that's worth a shot, although the measurement wouldn't be accurate I guess.
For example in case my real DPI wasn't dividable by 4 but you'd set the pointer sensitivity to 3, which would make the mouse go 1 px every 4 counts.
That would mean that my measurement precision would only be within the range of 4 counts if I thought this through correctly. Now if I only move one pixel too far left or right, that effect would increase. So for example in case I go 5 px past the mark, I'd end up with an inaccurated measurement of 20 DPI. It may be an answer, but right now, it's actually more accurate to measure in a game like CS:GO and deduce the real DPI in the calculator, which yielded far more consistent results for me even over the span of a few days.
Also, in a 3D environment, you could do stuff like limit mouse movement to horizontal movement only, or you could limit the amount the crosshair actually can move to a complete 360 (or any degree value) and provide a result like: "Mouse moved n counts to hit the mark. Mouse moved n+x counts until the end of measuring". You might even be able to tell the user not only the horizontal counts but maybe even the vertical counts that were sent .
Just a proposal though and thanks for the fast reply.
EDIT: It could also become a sellable feature for premium members, basic analyzer for free users, feature rich for premium users.