The SpecPhone is a 3D-Printed smartphone spectrophotometer for research and education. The device can make analytically accurate measurements of concentration and can be used for teaching analytical chemistry and DIY science projects.
For now it requires an iPhone 5, but new models will be made available soon.
More information at: smithlab.uakron.edu/specphone/
I strongly recommend printing in black PLA or ABS. This eliminates stray light and allows for cleaner spectra.