I came across 2 fun, easy apps that I have been using for /s/ articulation practice, but the apps could easily be used to address other goals. The apps are called Draw with Stars! and Hearts Extravaganza. Both apps were free at the time of purchase.
How do I use the apps?
The student and I take turns creating 'lines' of stars or hearts while producing a sustained /s/ sound in isolation (ex: "sssss..."). The goal is to work on sustained production of the sound and use controlled airflow. The student and I vary the activity in several ways: I draw a line, he/she draws a line; I make curvy lines, he/she traces over the lines; I fill the screen with about 10 lines, he/she erases the lines. I typically use this as a warm-up prior to practicing /s/ words. The students enjoy choosing hearts or stars (2 different apps), choosing the size of the heart or star, and choosing the colors. Students also enjoy making the hearts/stars fly off of the page (erasing).
Here is a pictures of some lines that I drew for the student (star app). To erase the stars or hearts (make them fly off of the page), touch the broom in the bottom right corner, then touch the hears/stars. It can be a bit finicky at times, just re-touch the broom and try again.