Lumiya viewer adds support for Google Cardboard. Inara has an article detailing it. There are some interesting user interface ideas.
Inara covers Radegast’s recent voice issues, a viewer apparently favored by the disabled.
VLC
You may or may not be aware of the VLC media player. It is a free, open source video player. It has basically replaced QuickTime in the SL viewers. The development team, VideoLAN Project has added the ability to view 360-video and pictures. See: VLC media player now supports 360-degree videos. Continue reading