From what I understand, Roll20 is not design to work on smart phone. However, some folks have reported that, if the DM has supporter status and therefore access to the mobile support, you can sometimes get it to work. It is a far less than optimal experience from what I've heard since the screen is very small and it's hard to take advantage of many of Roll20's capabilities. But, hey, no one's going to stop your friend from trying. Just be aware that it might be tough to use if it works at all. Good luck!
