Don't let your users get caught in a security web. Make it easy for them.
The Christmas Light Controller is a fun project that lets you provide public access to your outdoor lights during the holiday season.
MQTT is, by default, not secure, and many MQTT deployments seem to have missed the fine print when it comes to using MQTT securely. So let's exploit it.
I find the multilayered defense system built into many ancient forts fascinating. Fort D?n Aonghasa in Ireland is a great example of how a multilayered defense system was used.