The empire tree on the left hand side does this. A city that's not doing anything has a big gold border around it. Below the city picture are two bars, one for building construction and one for unit training, which show progress.

It may not give you specific turn numbers, but if all you need is to make sure you don't miss when something finishes, it does that. You can also hit the + button on the icon to expand the view, showing every garrisoned unit and every constructed improvement in that city.