In my bathroom I replaced the large bulb that is turned when switching on the vent with this bulb from Amazon: https://www.amazon.com/gp/product/B07TDP67LR/ref=ppx_yo_dt_b...

I use a small hand held concave vanity mirror and reflect the overhead light into my eyes. I wiggle the mirror handle to increase the spread. This is done while brushing my teeth since my electric toothbrush has a 3 minute timer.

Ergonomic ? yes. Practical ? for me yes. Safe ? maybe given the persistence effect matches what the paper said should occur. The Oxford paper used a small handheld red LED flashlight purchased for around $10 with a paper diffuser. I didn't enjoy doing it that way and stopped after a few attempts.

This bulb emits a lot of infrared light, probably its main purpose for the intended use. In Germany it is sold together with protective goggles for your eyes. So you should be carefull about the intensity of the light you put onto your unprotected eyes. With a reasonable distance it is pobably fine.

Please don’t look into IR light without proper protective glasses. Saves you from having to visit a ophthalmologist.

I'd imagine your eyelids and the sun.

https://www.piliapp.com/screen/red/ looks legit

LCD display red should be pretty close to 670nm

but just as the OP states that a monitor's blue is too weak to do harm, its red is also too weak to achieve the W/m^2 needed for therapeutic benefit

I picked up a great 670nm light from here: https://redlightman.com/

200+ for a red light? These are low power LEDs, not weaponized laser diodes. If you want a "deep" red LED then go to any hydroponic/grower supply store.

https://www.amazon.ca/HIGROW-Flowering-Fruiting-Spectrum-Enh...

Of course there’s a redlightman.com, but I am a bit surprised at the cost of these things. Is there something special about these “therapy lights” that a guy with a soldering iron and a handful of cheap 670nm LEDs wouldn’t be getting? I mean, the price of these finished products compared to my perception of the component costs is rather astounding.

This is the absurd reality anyone interested in led growing faces. And the saddest part is the uneducated fall for the many led scams out there. Many will advertise as 1000watts but then when you read the fine print they will say equivalent to 1000w. Or another good one they will name the model of the light “1000w LED Light” 1000w being the model of the light not the wattage. On top of it all many of these cheap lights are being sold for much more then they are truly worth to anyone. There are some reputable sellers who actually advertise the actual wattage used by lights but then you are really paying a premium. Like you said tho the reality is if you can solder these are easy to make. And if you live in the US you are really sitting pretty because all the parts are so cheap compared to me in Canada where I have to ship every part from the US. For about $600-$800US you can make a light that retails for closer to $2k.

Here is a very informative sight which goes over how to make several different led grow light builds ranging from 2x2 foot grow tent to an led for a 5x5. https://ledgardener.com/diy-led-strip-build-designs-samsung-...