Ask HN: Visual counting?

I'm wondering if anybody has heard of a general purpose application that lets you count things you care about in images. Think of counting people in marches, cars on a highway from a shot taken above or tree logs in a pile put together by a logger. Or maybe cells from a microscope image. Applications seem limitless.

It looks like advances in computer vision of recent years make such a product possible to make and I'm surprised I can't find a company doing "spreadsheets for the real world".

Have you heard of one or have ideas where to look?