SupportKit allows you to integrate a seamless in app messaging solution for your startup. Though it is mainly targeted towards mobile apps, it works splendidly on web apps as well. Your customers can send messages to you from within your website or app and this is pushed into slack channels for each of your visitors. It also integrates with other popular helpdesk services. It's totally Free for web apps and Free forever for mobile apps with 10,000 monthly users or less. It's a great cheap/free solution for startups to provide support for their customers through Slack and we're going to be using SupportKit in our our other startup.