1. A computer-implemented method for tracking user interactions with a mobile user interface (UI), the method comprising: collecting data while a user interacts with the mobile UI through a touchscreen, wherein the collected data includes tap-attempt data that specifies coordinates for touchscreen locations that the user has tapped while interacting with the mobile UI; examining the tap-attempt data to identify a cluster of tap attempts that are proximate to a non-tappable element in the mobile UI; and when such a cluster is identified, notifying a UI designer about the cluster of tap attempts that are proximate to the non-tappable element, to enable the UI designer to make adjustments to the mobile UI; wherein the collected data additionally includes swipe-attempt data that specifies coordinates for a “touch down” location and an associated “touch up” location for each swipe attempt, and wherein the method further comprises: comparing the swipe-attempt data with locations of swipable elements in the mobile UI, wherein each swipable element has an associated swipe target size; for each swipable element, using results of the comparison to determine a percentage of swipe attempts that have succeeded or failed for the associated swipe target size; and making the percentage information available to the UI designer to enable the UI designer to adjust swipe target sizes for the mobile UI.