The initial test of this idea was maybe two years ago -- so long ago that I was able to go to Radio Shack to buy some high(ish)-power PTH LEDs to test with:

It was a simple design based on work I had already done with 3D-printable crutch-handle-caps, LEDs, and parts from my parts bin:

I don't know the exact specs for the LEDs, but a page from Radio Shack's current web site is probably the same item: 7400mcd, 30 degrees, 30mA, 3.2v. Nothing amazing, but they did prove the concept.

I didn't think about the idea again until a few weeks ago when I saw this xkcd comic:

That got me to revive the idea, so that's why this project was started.