Getting your phone to take macro pictures by MacGyvering an external lens has been covered before several times at lifehacker by Whitson Gordon and Jason Fitzpatrick. User ASCAS posted his tutorial on Instructables, its pretty ingenious, and deserves a close look.
What makes this hack so unique is that the lens includes its own lens holder and the Images are so clear. To make the lens, you measure the size of the camera bulge on your phone using a circle ruler, then transfer your measurements to the LED lens holder. Trim to the resultant circle on the holder so it won't bulge out. Finally, cut some double sided adhesive to attach the lens holder to the phone and snap in the lens and volla!
Follow the link below to see the full DIY.