Ciphermail for Android - CipherMail for Android is an Android application which can be used with your existing Android mail...
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
Cellcrypt - Cellcrypt app provides features so you can enjoy secure conference calling, messaging, and sharing of documents.
Tutanota - Get your encrypted mailbox for free.
PGP Everywhere - PGP Everywhere is an iPhone / iPad app that allows you to utilize the security of PGP encryption anywhere you type, in almost any app!
Mailvelope - Mailvelope open source project. OpenPGP in your browser.