Peta Vision has Path on – Swipe to Type (iTunes Link) for the iPhone, iPod Touch, iPad in the iTunes App Store for FREE (regularly $1.99) for a limited time.

Now your pictures can have a thousand words with Path On.
Use crazy fonts to decorate your pictures with words, quotes, and lyrics, and
share it with your friends.

Don’t worry about restrictions, type whatever and wherever you want.

Draw a line with your finger and your text will appear along the line.
We also provide simple shapes, like a spiral, circle, or square. Our
app works great for anyone into scrapbooking, artistic photos, or even
just making fun pictures to share.

Path On features almost 300 different fonts–no additional cost and
unlimited use, of course– with the ability to adjust the size,
alignment, letter spacing, and more. With that many fonts, we
understand it’s hard to choose just one. That’s why we added a Font
Mix feature, so you can choose up to 5 fonts that will be randomly
applied to your text. You can also make your fonts stand out even more
by changing the backdrop or using one of our great filters.