We've had fairly good success with live video announcements, and have started experimenting with live on-location guests.
Our video switcher is OBS Studio, with the NDI Plugin for OBS. NDI (Network Device Interface) is a way of sending live video over a network with very low latency, and it has allowed us to do very cool things.
We use NDI Tools Scan Converter for remote cameras using webcams such as Logitech C920 webcam or Microsoft Lifecam HD 3000, or just the integrated cameras on Windows tablets.
A slides program or ProPresenter together with vMix Desktop Capture for NDI enables "over the shoulder" images, text, and video.
We also create virtual sets for our newsroom using Sketchup and Kykythea or by hand-drawing them, and use motion backgrounds from sites like Vidvo.
But one of the coolest things is that we can now have live video guests from anywhere in the world using Skype for Content Creators. The Skype output shows up as an NDI source that can be added to OBS, and the NDI Tools Virtual Input allows us to send any NDI source to the remote guest.
Soon we'll have on-location reporters using just phones on tripods.