Here is a photo of the rig I've built (3) to help you take your smartphone close-ups. Your phone sits on the top piece of Plexiglas and you position your camera lens over the disposable camera lens. The object you want to photograph sits on the bottom layer of Plexiglas.
The thickness of the plexiglass will cause some vignetting.
Use the zoom on your smartphone camera app to crop out the rough edges. Here is the same image "zoomed in". I used a backpacking headlamp to light the objects from below.
I switched to a red light for this image....
Make sure you bring items in to photograph!! I know you won't forget your phone. :)
There are a whole world of small objects just waiting for you to explore.
I used an app (free) called Snapseed to give this image it's rough look.
This is of the circuit board that was inside the disposable camera I "borrowed" the lens from.
In this image I placed the lenes between my Otterbox and my camera. I used Snapseed to saturate the colors in the image.
2/26/15 - I added this image today. I found that I eliminated the vignetting when I took my Otterbox off my Iphone. I placed a cheap ($1.00) LED light under the paper clips. I placed two sheets of blue tissue paper over the light to get the color in the background. (and diffuse the light).