Classical Location-based Services (LBSs) automatically derive the current location of known persons in order to select, compile, or filter location-dependent information and present it to their users. Zone services work the other way round: they estimate the amount of persons which are located in a given geographic zone and optionally obtain personal information from them in order to compile statistical information like the number of persons staying in a zone, their average age, and marital status. Zone services address a broad field of applications, ranging from emergency services to mobile marketing and research. This paper presents an approach for realizing such services by using broadcast technologies in combination with terminal-based positioning like GPS. Because data collected in this way always runs the risk of being misused, the paper also presents a framework that allows observed persons to define and enforce their privacy preferences.