In the age of mobile and ubiquitous computing, many nurses working in the healthcare sector still utilize traditional tools (e.g., paper calendars and clipboards) and pre-installed mobile applications (e.g., web browser, calendar) in their work activities. There exists a variety of mHealth applications, but none of them combines essential professional tools for nursing. We tackled this problem in the Finnish elderly house context through the User Centered Design (UCD) method whereby the target users actively participate in the design process. Together with 12 nurses, we first identified their profiles and their expectations on work-related mHealth application functionalities. The results were utilized in the conceptual design of Context-Aware Nurse Assistant (CANA), which combines the identified functionalities and provides contextsensitive services to consolidate nurses' work activities. This paper contributes to the field of ubiquitous healthcare as follows: 1) initial user survey that shows the need for CANA; 2) UCD design process of CANA and discussion of UCD's suitability for designing ubiquitous healthcare systems, 3) technical architecture based on modular web services and 4) evaluation results of a low-fidelity CANA prototype. These results are of interest to software designers, healthcare professionals and context-aware application developers.