Popplet is a mind-mapping software that has been around a while now. I found it useful in engaging pupils in their own understanding of connections between ideas and concepts and as a mind-mapping software it is very easy and simple to use.
I was asked a question today does it work on Chrome as well as iOS apps. Well there isn’t a chrome app but you can run Popplet through the browser which is the next best thing

The advantage of using the browser is that a teacher can show this and work on it class. I know that teaching styles prefer to work away from the board but I see value in having a session using the interactive whiteboard or screen to discuss hot topics