As great as the iPhone 4 camera is, it's not exactly ideal for macro situations. Luckily, you can build your own iPhone macro lens - with wire, glue and a disposable camera - so that it can be.
Instructable user RVogel decided to create his own macro lens for the iPhone and came up with a pretty nifty solution. Basically, he took the lens from a disposable camera and repurposed it on a mount to fit an iPhone (theoretically, you can create a mount to fit any mobile phone camera).
It's a pretty tough job that involves some drilling, sanding, cutting, bending wires at 90-degree angles and more, but after you're done, you can take pictures like this: