iOS devices with cameras only: We've shown you how you can paint with light using your DSLR or point and shoot camera, but getting in on the fun on your mobile was never really an option. Slow Shutter Cam fixes that by allowing you to take photos with slow shutter speeds. You just set the shutter speed you want — even the indefinite "bulb" setting is an option — and the sensitivity to light, then start snapping your photo. Slow Shutter Cam will handle the rest.
That said, there are certainly drawbacks when using a camera in a smartphone or tablet — even with one as good as the iPhone's. You'll definitely get better, more compelling results with a DSLR (or even a point-and-shoot) but with a little work you can actually paint with light using Slow Shutter Cam. We couldn't find an proper test in an office filled with light (and no dark areas outdoors) but were able to verify that the app can create photos with light trails by creating an ugly photo inside of a cabinet. It was just necessary to adjust the sensitivity to a fairly low level and play around with some of the other settings. The default settings didn't work so well, but so long as you follow the instructions for painting with light, Slow Shutter Cam will get the job the done with a few adjustments.
Slow Shutter Cam ($1.99, but $0.99 today) [iTunes App Store]