Stop Sign VR Tools has grown into a set of tools that run while you play a game. Each tool can be enabled and configured separately. Currently, there are four main tools and a few extras:

Cam Circle uses the headset cameras to show a live view of the real world in a circle in front of you. It has easy shortcuts and activates almost instantly. You can activate Cam Circle by double tapping the headset, or by pressing both grip buttons at the same time. Cam Circle is very useful for quick looks outside the headset and for picking up the controllers after putting on the headset. You can even set it to automatically activate when you put on the headset.
If you use a Vive Pro or Index, Cam Circle can show the pass-through video in 3D. On an original Vive it's monoscopic (2D). Cam Circle is not (yet) available for WMR or Oculus headsets.

Boundary++ is a new warning grid system that will show up when you approach your walls and ceiling. It works with native SteamVR headsets (such as Vive, Vive Pro and Index), Windows Mixed Reality (WMR) headsets, Oculus PC connected headsets and 'Mixed VR' sets (e.g. a WMR headset with Valve Index controllers or Vive Trackers). It will automatically import the WMR boundaries or Oculus Guardian (when using a Rift-S).
Boundary++ will not light up the whole play area, but it will only show where you are actually near your boundaries. It can be used together with the default chaperone, or just by itself.

Warning Boxes are virtual boxes that you place around your valuable real equipment, such as TVs, ceiling fans, room lighting and so on. They help you avoid hitting real stuff in and around your VR play area.
While you are playing a game a prediction algorithm warns you of possible impacts using sound, images and haptic feedback.
The boxes will fade out when you move away from them. The fade-out and full-visibility distances can be configured for each box separately.
If you can't find your boxes because they're faded out, press the system button and look around.

The HUD is a Heads-Up Display that will show up when you are moving backwards into a wall or other boundary object, such as a Warning Box.

Extras and other info:
-> The tools run alongside other games.
-> A box can be configured to show content by other overlay apps. E.g. a box can show the fpsVR overlay on one of its sides, or it can show the content of a Desktop+ overlay.
-> Do you use a Mixed VR set and experience grey screens with seated games? This app has a fix for that problem. You can find it on the Boundary++ settings page on the SteamVR dashboard.
-> All basic settings are accessible on the dashboard pages for Stop Sign VR Tools. Next to the basic settings there are many things that can be configured and fine-tuned using the separate Settings Editor program in Windows (not in VR). Also use this Settings Editor to add more virtual boxes, delete or edit them. You can start the Settings Editor from the Windows System Tray, next to the clock in the bottom right corner of your desktop.
-> The Stop Sign VR Tools runtime is 100% coded in C++ and optimized to spend very little CPU/GPU cycles. It does not harm the performance of other VR software.
-> The alert sounds are spatialized by Steam Audio's HRTF-based binaural rendering so you will hear where the closest wall or object is, even if you can't see it.
-> You can find a few YouTube videos here: https://www.youtube.com/channel/UCRsqrIQ34-BVTNf4nGpzWbQ