[General Questions and Answers] GaloA:
** I wanted the same thing for a headset

Found a workaround using 2 Android phones (#1 for the HUD (android or iphone) and #2 (only android) to mirror from),

i screen cast to a website, visit that website on a second phone, and apply a CSS snippet that reverses/flips/mirrors what's on the website.

The steps:

1 ) On the #2 phone install the 'Screen Mirroring & Sharing' app:

Screen Mirroring & Sharing - Apps on Google Play

Screen Mirroring - Fast & Simple! Share screen and cast to tv or other devices!

play.google.com

This lets you mirror your phone screen to a browser website (both phones need to be connected to the same wifi network (or mobile hotspot) )

2) On the #1 phone install Mozilla Firefox.

3) On the #1phone, in Firefox, install the Simple CSS Inserter addon.

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4) In the Add-ons menu (you get to by clicking the three vertical dots menu) click on Add-ons manager at the bottom.

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5) Click on Simple CSS Inserter

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6) Click on Settings

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7) Paste the following CSS code in the text box:

body{ transform: scaleX(-1)}

*** Edit: for a HUD you might have to change this to scaleY(-1), to flip the screen up down (along the vertical axis), like this:

body{ transform: scaleY(-1)}

haven't tried this, but i think it should work!

8) Click on Save CSS (make sure Insert CSS on load is 'Off')

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9) On this #1 (HUD) phone, head on over to: http://www.screenmirrorapp.com/

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10) Now, pay special attention: with the #2 phone (the one that will be mirrored) open the Screen Mirroring app.

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11) After all the adds, and the app asking you to review it, click on Browser Mirroring.

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12) Click on Start Mirroring.

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13) With the #2 phone, scan the QR code that appears on the website from step in phone #1.

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If all goes well, you're mirroring the #2 phone on the #1 phone.

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14) Now, on the #1 phone, press on the three dot menu in Firefox.

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15) Click on Add-ons.

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16) Click on Simple CSS Inserter.

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Now the screen mirroring should be reversed along the x-axis. Voila!

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Now you can press on the full screen icon to maximize the screen:

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From there you can set the appropriate rotation settings on both phones. Place the HUD phone in the HUD holder/reflector. Open up Google Maps or which ever phone, and you're good to go!

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The advantage is that you can always pick up the #2 mirror phone to receive a call, set a route, play music, and the screen won't be reversed/mirrored/flipped!

A lot of steps for the first time. After that you can add a shortcut to the page on your home screen (phone #1), click on this shortcut, open up the app on phone #2, open browser mirroring, click on Start Mirroring, scan the QR code and thas it!

This should work for a teleprompter too.

I'm sure anyone that is able to make a screen mirroring app with react native should be able to implement this functionality.

Anyway, hope this helps! 👍