Why would you assume the cycle is regular? It’s a biological process that can vary quite a bit, which is part of why you would want to track it in the first place. There’s also much more to track that just the expected start date of your next cycle. The various tracking apps are quite a bit more involved than just a calendar.
This had never occurred to me before but it’s great, thanks! I expect that alarms don’t run until after first unlock, so 3am wouldn’t be great if I use the phone to wake up but later in the morning should be good.
The article is very misleading. It says
The research paper…notes that the human body is particularly efficient at generating 40 MHz RF energy. Tapping into that through a ‘worn receiver’ provides power without using any invasive means.
But I read much of the pdf linked at the bottom of that link, and there’s nothing about the human body generating energy at 40MHz. The trick is that skin is pretty effective (sort of) at conducting energy at that frequency, so the authors hooked up a power transmitter worn on the forearm, 5 or 15cm away from a receiver on the hand.
This isn’t about powering anything by body energy, it’s about strapping a battery-powered transmitter somewhere on your body and then having another device pick it up when strapped somewhere else on your body. No thanks.
Oh and it’s actually pretty inefficient and won’t provide much usable energy.
Actually I’ll agree with you that a spreadsheet could do a lot, but that’s a niche solution. Building a good one requires a fair bit of technical know how, and even using one well requires a lot of understanding.