From Hackaday.io:
“This project grew out of a common source of frustration at our office: we have only three toilets for ~70 employees, and there is frequently contention for this scarce resource. There’s nothing worse than patrolling between the three restrooms searching for an open one.
“A co-worker, [eben], and I started brainstorming how we could solve this issue, and an IoT device seemed the obvious solution. During some booze-infused brainstorming sessions, we came up with the architecture for this, and built it.”
All the details here.