OPlayer Lite is currently one of the best video players for iPad. It has excellent support for almost all formats (the latest update includes MKV support too). There’s an AC3 issue with the current version though — still, a far better player than many others out there. The decoding can be particularly tricky with other apps, but Oplayer appears to handle it quite well.
Signal Private Messenger is one of the most popular privacy chat apps. It features end-to-end encryption for all messages, voice calls, and video chats between two Signal users. It focuses a lot on individual chats. There are group chat features, but it's mostly for personal use. This is one of the biggest differences between it and rival privacy chat app Telegram. Video calls worked fine in our testing so we have no trouble recommending them. It's a neat way to get some encrypted chats as well. The app is also completely free and open source. You can't really go wrong with it, but there are better video chat apps if you need group video chats.