From Cerulean Studios:
Trillian is an instant messaging app that works on phones, tablets, and desktops while keeping your chats neatly synchronized between all of them! We think conversation should be easily shared between all of your devices, not trapped as text messages on your phone. Here's how we do it: INSTANT MESSAGING: Your unique Trillian username can be used to send unlimited messages free of charge. Trillian uses your existing data plan and/or WiFi. ANYWHERE: Trillian's continuous client feature delivers your chats instantly between all of your connected devices. In addition, Trillian automatically silences push notifications on mobile devices if you're active on a desktop - no more dealing with a phone buzzing on your desk all day! SIMPLE: Trillian places a strong emphasis on fast and reliable message delivery and a beautiful, easy-to-use interface. SECURE: All communication with Trillian servers uses TLS to ensure third-parties can't read your chats. INTEROPERABLE: Of course, Trillian wouldn't be Trillian without support for Facebook Chat, MSN, Google Talk, AIM, ICQ, Yahoo!, and Jabber.
What's new in this version:
Infinite scroll for message history, voice clip sending, minor improvements and bugfixes. Full changelog: https://www.trillian.im/changelog/ios/3.1/