You can see I've massaged my lens quite a bit. I bent the good lens so it was flat, cracked off the other lens, then shaved it down a bit with some wire snips. I then drilled two small holes in the arm and used an exacto knife to connect the holes, making one slot. I also snipped the arms of a paper fastener. I'd have liked to have a smaller one but I used what was at hand. I then poked a tiny hole in the case as seen on the ridge. (by the way, I got the case at 5 below for $5 so not worried about it too much).
Next slide the fastener through the lens and case hole and spread the paper fastener's wings so they curl into the case. Put a piece of transparent tape over it to discourage scratching the iPhone (you could use something industrial but I wanted to keep up the clear case effect). Now just slide the lens over the camera whenever you want to use the macro!
I'd like to have mounted the lens inside the case and cut some of it away, but I thought I'd quit while I was ahead.
Also note that the app SnapTell (AppStore link)
is pretty fantastic-- it basically bypasses barcodes and does image recognition on pictures you take of objects. Basically a Shazam for products. Right now it's only for CDs, DVDs, and games, but can you imagine what either of these technologies could do for grocery shopping!?