In an aging society where millions of older adults face loneliness, cognitive decline, and limited emotional support, there is a growing need for digital solutions that go beyond clinical care. WithU is a compassionate, AI-powered mental wellness app designed specifically for seniors, caregivers, and families.  This paper explores the system design, functionality, and user experience, while also addressing key limitations such as AI sensitivity, accessibility for cognitively impaired users, and the need for deeper family and healthcare integration. Experimental evaluations of AI feedback across nutrition and mental health scenarios reveal both strengths and blind spots, guiding future improvements. Ultimately, WithU seeks to redefine digital eldercare by creating a space where older adults are not only monitored but meaningfully supported—emotionally, cognitively, and socially.