This seems like an obvious idea for a little utility, so I'm wondering if someone has one already. I would like a utility in which I can click on the mouse twice, and the utility simply tells me how many frames pass in the interval between clicks. There would be a box to enter the frame rate, then you just go click-click, and it says "That was 37 frames" or whatever. The Pro version

could even measure the intervals between more than two clicks, and go in the reverse, where you enter the number of frames and it flashes twice to show you how long that many frames is.
Is anything like that out there? I am currently thinking "Bonk........Bonk" in my head, then guessing about how long that interval is and multiplying by 24, dropping keyframes and dragging them around. Which is fine, I just thought this would be a more elegant way to do it.