Inclusion Criteria:  65+ years old English speaking; resides in local Los Angeles area or the Pacific Time Zone; self-reported memory or thinking problems that score within a range of mildly impaired on a cognitive test or a clinical diagnosis of cognitive impairment ranging from mild cognitive impairment (MCI) or mild dementia (of any form). Mild dementia is the top end of this clinical diagnosis range. MCI is the low end of the range. reports <150 minutes of moderate to vigorous physical activity per week as per a single-item screener; self-reported ability to safely engage in regular walking; smartphone owner of a compatible smartphone for ≥1 month; willing and available second family member/friend/caregiver who owns a smartphone and can attend training sessions; and observed ability to reliably access and operate a smartphone during training.  Exclusion Criteria:  unwillingness to meet at local community venues and/or via online meetings unwillingness to comply with study procedures for the length of the study inability to participate in English. residing outside of the local Los Angeles (LA) area and do not have the capacity to participate remotely or commuting to the University of Southern California (USC) study site recent cognitive status does not fall within an acceptable MCI/mild dementia range as determined through Montreal Cognitive Assessment (MoCA) if diagnosis was unverified by health care provider or by ADRC or memory and thinking problems were self-reported recent cognitive status is below what is acceptable for MCI/mild dementia as determined through MoCA if diagnosis was verified by health care provider or ADRC