We recently completed a project in which we needed to popup a tooltip-like box when hovering over an element. The :hover CSS pseudo-class works fine in desktop, but not so well on mobile. What ends up happening on mobile is that tapping the target element does indeed pop up the tooltip, but tapping elsewhere on the screen fails to close it. Clicking another link or hoverable element does the job, but we needed to emulate proper lightbox/tooltip behavior, in which clicking anywhere else will trigger it closing.
What we ended up with is the following jQuery/CSS combo that seems to do the trick nicely.