Identify the tasks that need to work on a phone: accounts, bookings, orders, notifications or staff workflows. Decide whether a responsive website, progressive web app or store-distributed app best fits the audience.
Agree device support, permissions, data synchronisation and connectivity requirements. Offline behaviour needs explicit rules for what is stored locally and how conflicting changes are handled when a connection returns.
Test core journeys, error states and account access on representative devices. App-store accounts, reviews, external fees and approval timelines are provider dependencies; release and maintenance responsibilities belong in the proposal.