TLDR; Build an android address book application that stores data in a decentralized fasshion.
Android devices usually come with the pre-installed Android and Google Address books. However these address books are not easily syncable with other devices, they are not encrypted and most importantly: hosted by Google.
In Consento we also have contacts and addresses and it may be a good idea to deeply integrate with the Android operating system as it allows for deep integration, whereles iOS does not.
A simple android application that syncs all contacts from the address book. It stores the addresses in an encrypted fashion and acts as an address book provider. Additional decentalized identifiers allows backing-up those addbooks in a hypercore pinning service.