I've read all of these threads about tool height center gauges and many of them look quite impressive but the old faithful Starrett 60° thread center gage has been my old stand by forever. it has such a multitude of uses which I find well within the range of accuracy for many things I do that I hardly ever need to set up a Di center locator except for when doing a set up on very small parts or on the vertical mill
Nice alternate design though, not sure how well it could be incorporated when needing to change tooling while a long cylinder is chucked between centers unless it can be placed on the cross slide as well, Nice feature with the beeper but I doubt if I would be able to hear it although a low intensity LED light might be the ticket