for my app I want something like the account check in whatsapp.
I mean, when you open your address book in whatsapp you see which user had an existing whatsapp-account.
I know how to get access to the local address book and from my provider (backhand.com) i could receive the registered email-adresses for my app.
But i don’t know how to check this?
I think the only way is to transfer the contacts (hashed) to the server, right?