Yesterday I needed to document some phone/data jack numbers and ran across a couple behind office furniture with only a two-inch clearance, fairly dark and with no clean line-of-sight.
But I was armed with my swiss-army-knife, app-loaded smart-phone. I first tried the Color Flashlight app to illuminate the area, but the viewing angle was too severe. Second attempt was the Camera app, but the picture turned out way too fuzzy due to its long focal length. But if the normal camera has a longer focal length, perhaps the front-facing "Selfie" camera was shorter. Bingo! Success, as shown in the photo below.