Technology for care at home is an important factor in supporting our ageing population. These technologies need to be both accessible and acceptable to a wide variety of users if they are to be taken up and successfully used in people's homes. This paper describes the user-centered co-design and evaluation of a multimodal reminder system for the home deployed on mobile devices. Six co-design sessions (N=25 users) were carried out with groups of older users to investigate the best methods and techniques for configuring reminders and how they should be delivered within the home. Both sketches and implemented prototypes were used to gather qualitative feedback on a variety of interaction features and techniques to find what worked best for an older user group. We present the findings from the sessions in terms of the re-design of a personalisable multimodal reminder system. We also present the co-design process used and go on to discuss the value this method adds to the design and evaluation of home care technologies for older users.