The best alternatives to Simplicity Blocks are involve.me, FlowXO, and HipChat with Your Users. If these 3 options don't work for you, we've listed a few more alternatives below.
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LaunchDarkly— Helps devs ship faster and safer with feature flags
We are building scalable promotions engine which businesses integrate with to provide a personalized shopping experience to customers. Our APIs are available here https://stack.promo/api/index.html and guide is here https://stack.promo/how-it-works.html