Clerk - Clerk.io, the artificial intelligence for e-commerce that knows your customers interests.
Twilio for Slack - Enable SMS conversations with Slack+Twilio
Spike.sh - Spike is an incident management platform that alerts via slack, phone and email and automatic escalations to help teams fix infrastructure problems.
MailClark - The Slack bot for external communications
WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Clerk Chat - SMS for Slack