The demographic development indicates an increased elderly population in Sweden in the future. One of the greatest challenges for a society with an ageing population is to provide high-quality health and social care. New information and communication technology and services can be used to further improve health care. To enable elderly persons to stay at home as long as possible, various kinds of technology, such as safety alarms, are used at home. The aim of this study was to describe the experiences of elderly persons through testing a mobile safety alarm and their reasoning about safety, privacy and mobility. The mobile safety alarm tested was a prototype in development. Five elderly persons with functional limitations and four healthy elderly persons from a pensioner's organisation tested the alarm. The mobile alarm with a drop sensor and a positioning device was tested for 6 weeks. This intervention was evaluated with qualitative interviews, and analysed with latent content analysis. The result showed four main categories: feeling safe, being positioned and supervised, being mobile, and reflecting on new technology. From these categories, the overarching category 'Safety and mobility are more important than privacy' emerged. The mobile safety alarm was perceived to offer an increased opportunity for mobility in terms of being more active and as an aid for self-determination. The fact that the informants were located by means of the positioning device was not experienced as violating privacy as long as they could decide how to use the alarm. It was concluded that this mobile safety alarm was experienced as a tool to be active and mobile. As a way to keep self-determination and empowerment, the individual has to make a 'cost-benefit' analysis where privacy is sacrificed to the benefit of mobility and safety. The participants were actively contributing to the development process.