Their privacy policy lists what they collect, and it’s a fairly large amount of stuff.

Copy/paste from their site:

What data does Beeper collect?

In order to provide the service, Beeper collects device information, including OS, hardware, public IP addresses, network routing information, information on the installed Beeper client, and other device settings. Beeper also uses user account information, such as email addresses and phone numbers, to authenticate users to their accounts.

See our Privacy Policy for more details on how we collect and use personal information.

Now, that isn’t exactly what I’d call privacy friendly. However, for something like Facebook messenger, it isn’t any worse.

I intend to at least try it out if they ever send me the damn email to let me use it at all lol. But that’s primarily to see how it interacts with imessage for the folks I know that use that. I’m not going into it hoping for security, since they dick around with encryption in a way that breaks it.