We wanted to verify if was possible to use Amazon's App Store to download Apps, even those that require payment, so we decided to try to download iDisplay, and App we know works well on the R-7.
Below is a link to APK for Amazon Underground, an older version of the current newly released Amazon App Store; download & install it on your glasses, and make sure to go to Settings->Security and turn on Unknown Sources to allow it to run.
You need to run this older version of the App to download their new App Store. Here are some screenshots (sorry about the aspect ratio being wrong!)
Install Underground on an R-7 running our latest OS (4.3.8) and run it.
Once logged in with a valid Amazon account, search for iDisplay. When an attempt is made to download it, you will be prompted to download the newer Amazon App Store App:
Click Install Amazon Appstore, and it install it and then searched again; It looks like this:
If you clicked on the $17.95 button, the App Store App will download & installed it:
In end, there were the 3 Apps loaded onto the glasses:
This method works, though it would be simpler to download & sideload the latest version of Amazon App Store directly. If someone locates an APK of the New App Store, let us know.