Touch and Write is an app that helps children practice writing in a fun way using 16 different writing textures. These include shaving cream, grape jelly, chocolate pudding, and many more. While writing the letters, you not only see these textures, but hear the actual sounds they make. Aside from the "pens", there are also a variety of "papers" to write on. 
In addition, there is a guide to help younger children form shapes and letters which can easily be turned on/off in the middle of the activity.
There are also preset wordlists such as high frequency words, animal names, word families, as well as a "make your own" wordlist feature. Touch and Write is available in cursive and Hebrew too.