Two Star rating out of five. ★★
Ostel is a tool for having end-to-end encrypted phone calls. Our goal is to promote the use of free, open protocols, standards and software, to power end-to-end secure voice communications on mobile devices, as well as with desktop computers.
It’s a paid app and for $6.99 you’ll be able to receive encrypted calls. There’s an additional $24.99 in-app purchase for the ZRTP extension to also place a secure call.
It has an OSTN setup wizard to make life easy. You’ll only have to enter your name, password and ostel.co and you’re ready to call!