I think the Polaroid ZIP Mobile Printer is pretty amazing. It has wireless printing technology and connects directly to your phone via bluetooth (compatible with both iphone and android). It also comes with a USB so you can also connect to your digital camera or computer if you'd like, and a free download of the Polaroid ZIP app to make editing your pictures before printing super easy. The photos are 2X3, and printed on ZINK paper, which is easily refilled via Amazon.
I love scrapbooking, but get behind with printing photos from my phone. I love this gadget because it's so simple, portable, and reasonably priced that I can print photos for scrapbooks or art projects whenever the mood strikes. Which is often! I also really like the idea of stocking up on some extra packs of ZINK paper and bringing this with me to a party or get together, and then giving out the photos as little mementos of the day.