TiltShiftGen
I’m testing out an iPhone app called TiltShiftGen (99ยข, iTunes link), a simple app that allows me to apply tilt shift filters to images on my phone, and I’ve been thrilled to have found it (thanks to @iamkory for the recommendation).
You are able to either use an existing photo in one of your albums, or take one from within the app itself. Then you have the opportunity to apply a variety of specific filters, such as a linear or circular blur, adjust the image’s saturation, brightness and contrast, and even add a dark vignette. The result is a photo that looks like it’s been transformed from a normal scene to a view of a miniature, through the clever use of blur and color.
Here’s a shot I took just a little while ago at the park with the family:
And here’s the same shot, but with the TiltShiftGen filters applied:

Your finished result can be emailed or sent out to Twitter, though support for specific iPhone Twitter apps is lacking. You also have the option to save the image to your camera roll, preserving the original file for later (unless you have taken the photo from within the app itself – this seems to leave you with only the finished copy).
All in all, though it’s a great app to add to your iPhone if you take lots of photos and want to breath new life into them, so be sure to check it out.
The ONLY drawback is the small output resolution, but the developer has always been very responsive to feedback, so I expect it soon