Normally, mosaics are a job for the desktop computer. Software has to look at a photo, examine the bright/dark areas and finding pictures that reflect the right coloring. An app that does basic cropping and image filters also offers several levels of mosaics.
The app, Fotoyaki, is a free iPhone app that produces some very interesting effects. Like any specialty photo app, some pictures produce great results, others not so much. The free price of Fotoyaki means it’s on my iPhone that I toss pictures at to see what works.
Along with the mosaics processing, there are also to levels of dot effects that can really be fun. The Fotoyaki dots have proven to work best on images I have taken with straight lines. Sharing the finished result is done by saving to the iPhone photo library, email, Twitter and Facebook.