It's even more difficult when alternatives are so scarce. For example TextSecure doesn't exist for iOS.
There might be iOS version, but there very likely never will be web version, or FxOS version or desktop version or anything like that.
Which is really sad, because unlike Telegram authors, TextSecure's author is very good with crypto.
[1]: it's a long read: https://github.com/WhisperSystems/TextSecure/issues/127