As of 2015, there is an app for iOS called Word Collage that works on both the iPhone and the iPad. WordCam! is an option for Android. Wordsalad is a free alternative app for iOS and Android that creates word clouds.
For iOS, Word Collage creates a collage based on a particular defined text or a website URL. It claims to support creating collages in different layouts, fonts and colors. Similarly, Wordsalad claims to offer the ability to create word clouds with customized fonts and colors.
A version of Wordsalad is also available for Android. In addition, the app WordCam! is available for Android, and it can take a gallery or camera image and recreate the image using a series of words, creating a word collage in the shape of the image.