1. A graphical user interface for presenting advertisements to a user on a display of a mobile communications device, the graphical user interface comprising: a display of a mobile communications device; a first graphical user interface window for displaying content on the display of the mobile communications device, wherein an advertisement delivery sub-application is embedded in the content, wherein an activatable graphic element for the advertisement delivery sub-application is displayed in-line with the content, the activatable graphic element providing an indication to the user that an advertisement is available to be viewed upon a request by the user; a second graphical user interface window configured to partially cover the first graphical user interface window in response to the request by the user to display the advertisement, wherein the request by the user is a first external input received on a first input modality of the mobile communications device, the first external input corresponding to a triggering of the activatable graphic element for the advertisement delivery sub-application; wherein the second graphical user interface window displays advertisement invocation instructions prompting the user to provide a second external input in response to receiving the first external input corresponding to the triggering of the activatable graphic element; and wherein, while receiving a second external input on a second input modality of the mobile communications device different from the first input modality at the prompting of the user, the second graphical user interface window displays an input progress indicator, and after receiving the second external input, the second graphical user interface window displays the advertisement separate from the advertisement invocation instructions upon an evaluation of a substantial match between a set of quantified values translated from the second external input to a set of predefined values corresponding to the advertisement invocation instructions.