Signal seems to consider that Chrome extension a 'Desktop Client'. Which it isn't, and unfortunately it won't help users that aren't using Chrome (a lot of my non-technical friends are on Edge now with Windows 10, the rest is split roughly 50/50 between Firefox and Chrome).
Signal, with decent support for multiple devices (and ideally: Without requiring a phone number!) would be awesome. Until then, Telegram works best for me.
I mean, are you interconnected with something (Signal interop a-la WhisperPush on CM? XMPP with OMEMO and GCM/APN via XEP-0357? Telegram network with Axolotl overlay? Something else?) or you're yet another proprietary standalone network?
Protocol, for example: https://github.com/actorapp/actor-platform/tree/master/docs/...
* Signal - the crypto * Ricochet - no metadata leaking * Burner - the ability to have multiple IDs without trying to tie to PII
Last but not least, a commitment to have Actor code evaluated by credible outside security firm.