EagleEye lets you see more detail without zooming in and a broader view without zooming out. It does this by creating a "popup view" next to the cursor when holding down both a control & shift key. When the keys are released, the popup view remains, letting you place datapoints (or snaps, resets, etc.) with more precision. The popup view goes away when it is not being used.
Download the latest version here.
Price: Free!!!