A bit off topic, but what I've wanted forever and never found is a spreadsheet that deals in units natively. So if one cell is in Newtons and I divide it by a cell that is in m/s^2 I want the resulting cell to be in grams. Units should propagate through the sheet automatically. Unit prefixes can either be automatic (km, m, mm, um, etc) or fixed as you would with a format setting.

Google calculator is the closest thing I've seen to this, but it isnt in spreadsheet form.

Anyone know of a system that provides this functionality?