1. OtrkitAn Objective-C Off-the-Record library for iOS.
3. Apns ClientPython client for Apple Push Notification service (APNs).
4. Chatsecure IosChatSecure is a free and open source encrypted chat client for iOS that supports OTR and OMEMO encryption over XMPP.
7. RubDubA Node XMPP Push Service for XEP-0357: Push Notifications