VutalkGet Vutalk
One app that adapts to the version of iOS it runs on, so there is only ever one thing to install.
Android
In development
An Android client is on the way.
Desktop
In development
A desktop client that links to your phone is on the way.
What you need to sign up
An email address that can receive a verification code. That is all — there is no phone number step and no SMS.
Set a username afterwards if you want people to be able to reach you. Without one you can still start conversations yourself; nobody can start one with you.
Sign-up
Email address
Verification code
A username, if you want one
Never asked for: phone number, contacts, real name.