What are some alternatives?
When comparing Bizpopuli and Invision, you can also consider the following products
UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
UserEcho - Online customer support solution - Feedback Forum, Helpdesk (ticketing service), Knowledge Base and Live Chat by UserEcho
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.