Fwiw i built one of these using an S2 host and a Samsung emitter. We have a daughter with a condition and monitoring for rashes is important, household lights tend to not be good enough.

First, the s2 kind of sucks in this role. Its big and the removable battery is annoying. This woukd be better with a usb battery but better yet would be usb direct or even just contact points.

I would love to see a proper pen light with a no-optics 519 or a large emitter led with a high r9. Call me crazy but i really like optics free led lighting