This paper presents observations and participatory design meetings to determine desired properties of new mobile phone-based memory aids for seniors. We observed a clinical population of individuals with Mild Cognitive Impairment (MCI) participating in a memory intervention session for a period of six weeks. We then conducted a series of participatory design activities with five normally aging seniors who were concerned about memory loss. Based on these two activities, we contribute evidence that mobile PDA phones contain many of the properties that seniors desire in an external aid; however, they lack appropriate software and hardware. Mobile phone designs should be changed to accommodate seniors, but only in coordination with better user support and without removing desirable memory support functions.