Breastfeeding is positively encouraged across many countries as a public health endeavour. The World Health Organisation recommends breastfeeding exclusively for the first six months of an infant's life. However, women can struggle to breastfeed, and to persist with breastfeeding, for a number of reasons from technique to social acceptance. This paper reports on four phases of a design and research project, from sensitising user-engagement and user-centred design, to the development and in-the-wild deployment of a mobile phone application called FeedFinder. FeedFinder has been developed with breastfeeding women to support them in finding, reviewing and sharing public breastfeeding places with other breastfeeding women. We discuss how mobile technologies can be designed to support public health endeavours, and suggest that public health technologies are better aimed at communities and societies rather than individual.