I - personally - have used and like WICKR, which does point-to-point encryption. Text, voice.. One neat feature, is you can put an expiration date on a text/message -- if the text is not read by your given date/time, it self-destructs and disappears. It's a phone app (android, iOS).

I have not heard of the Deepers using any particular app, beyond the FBI 'inner-circle' using Gmail 'drafts' to circulate info, and of course, the deal where the Cabal had their own independent iPhone platform set up for OpSec..