Enter the project (all of which is open sourced under an MIT License), which took good month working some nights and weekends this summer to complete: BORAT: Bathroom Occupancy Remote Awareness Technology. BORAT is an Arduino-based toilet occupancy notification system. It uses inexpensive wireless radios (nRF24L01+) to communicate occupancy status of one or more bathrooms to the main display unit located in a highly visible area. You may be asking — why in the hell does the observer unit (which determines occupancy) need sonar? Well, if you’re like me, you like to take your time when you are …​ you know. Perhaps I don’t move very much during this time. Maybe I’m reading my phone. This would cause the motion sensor to eventually give up and show a green light. This is where sonar comes in. Aimed directly at someone sitting on the toilet, sonar will read a different distance with a person there versus without. You can configure the threshold after installing Observer, and — voila! Near 100% accuracy! Is it creepy to have a 2-eyed robot staring at you in the bathroom? I’ll leave that question to the reader.