What are some alternatives?
When comparing Sketchboard.io and Stormboard, you can also consider the following products
Walling - Walling is your visual space to capture ideas and organize projects.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Jamboard - Interactive Business Whiteboard | G Suite
XMind - XMind is a brainstorming and mind mapping application.
DrawAttention - A whiteboard for you laptop lid
MindManager - With MindManager, flexible mind maps promote freeform thinking and quick organization of ideas, so creativity and productivity can live in harmony.