ContactCast allows you to mutually share contact cards with others to keep all your contacts up to date. You simply only manage your shared contact cards and everyone you shared it with will always have your up to date information.
The way this works is you create a new contact or select a contact from your address book and then share it with others. They get an invitation link which opens the app when the invitation is accepted and then they can see the contact you shared with them. You can update the contact card anytime you like and all changes will be reflected on the devices of the people you shared it with.
You can particitpate in the beta test here.