We present the iterative design of Momento, a tool that provides integrated support for situated evaluation of ubiquitous computing applications. We derived requirements for Momento from a user-centered design process that included interviews, observations and field studies of early versions of the tool. Motivated by our findings, Momento supports remote testing of ubicomp applications, helps with participant adoption and retention by minimizing the need for new hardware, and supports mid-to-long term studies to address infrequently occurring data. Also, Momento can gather log data, experience sampling, diary, and other qualitative data. Author Keywords Mobile Devices, Wizard of Oz, Rapid Prototyping, Experience Sampling, Diary Studies ACM Classification Keywords H5.2 [Information interfaces and presentation]: User Interfaces. - Graphical user interfaces. General Terms: Design, Human Factors, Experimentation