The paper presents details of the AAL Call 4 EXO-LEGS project aimed at developing and testing lower body assistive exoskeletons to help elderly persons perform daily living activities independently such as stable standing, sit-to-stand transfers and straight walking. The key components needed have been realized using mobility requirements and design preferences provided by an end user group comprising 118 members via 5 surveys. Modular human-centric concepts are followed for mechanical design, sensing and actuation, system integration, etc., to realize a BASIC exoskeleton prototype able to provide up to 30% power to assist the human perform the intended motions. Two ethical approvals have been obtained to involve end users in the research, development and test phases of the project. To date, 5 test subjects have tested the exoskeleton prototype in walking and the sit-to-stand test; summary results are presented in this paper.