NOTE: NEW UPDATED LENS INFORMATION (as of 9/24/15). PLEASE SEE LENS INFORMATION BELOW
Make your own macro lens adapter for the iPhone 6 and 6+ (This design fits both phones). I designed the original version of this for my iPhone 4 (see "iPhone 4 Macro Lens" here on Shapeways) when I couldn't find the close-up image quality I wanted, even at $60. You can make your own with the surplus lens I found (see below) and, in my opinion, get better image quality.
Check out the example photos (unfortunately Shapeways compresses them and limits size) as well as the orginal models for the iPhone 4/4s and iPhone 5/5s:
iPhone 5 Macro Lens
iPhone 4 Macro Lens
PLEASE NOTE: This model will not slide over iPhone 6 and 6+ cases. It fits only on an uncovered iPhone. Here is a link to one that fits over cases.
iPhone 6/6+ Macro Lens for iPhones with cases
Print this model and then buy a glass lens for $4.50 from Surplus Shed http://www.surplusshed.com/. Their part number is L13906 (NOTE - THIS IS NEW UPDATED LENS CHOICE. The previous L4581 is sold out, so I have changed the design to fit an 11mm lens). The search function on the Surplus Shed site won't search part numbers. To find L13906, use the "Lens Finder" on their homepage.
In "Lens Finder" type:
Lens Type: PCX, Plano Convex
Diameter: 11mm to 11mm
Focal length: 49mm to 49mm
That will get you to L13906. If you want other magnifications, search for other 11mm diameter lenses. A longer/shorter focal length means less/more magnification. Feel free to experiment.
The lens fits in a 11mm recess in the Shapeways model and is held in place with a drop of Superglue. If you get any glue on the lens, it can be cleaned off with nail polish remover or acetone.
NEW EASIER ASSEMBLY INSTRUCTIONS !
The lens is plano-convex (one side is flat). When inserted in the model, the flat side of the lens should face the phone. Press the lens into the opening before applying any glue. Make sure it is seated all the way against the support ring at the bottom of the hole. Again, do this first WITHOUT glue. Once you are sure the lens is properly seated, squeeze one TINY drop of superglue into the seam between the lens and the plastic holder at two spots on opposite sides of the lens circle (from the front). Two drops should be enough. The drop should wick around the edge the lens by itself so you won't need to spread it around. Let the assembly sit for 5 minutes before doing any lens cleaning.