The PIR sensor if probably the part that gives me the more difficulties and I'm still unsure. I started by looking at what Fibaro uses:
It's an Excelitas PYD1698. It looks like a great chip, low power, everything included... But it seems nearly impossible to source in low quantities. I was not able to find a datasheet. Maybe it's worth sending Excelitas an e mail, but by experience, I don't have that much hope.
Then I found the exotic chip E93196. It has everything in it, is low power, digital communication, and gives you a programmable interrup, for good price. Datasheet says 8µA : http://www.hsinbao.com.tw/administratorHB/caproduct_data/pdfs/E93196_12_wm IG.pdf
I'm balanced between simplicity and low power choices. Standby currents for about every sensors I choose seemed "good enough" compared to the global consumption. I first tough of multiple power rails, I could go as low as 2.5V, but then I can't use the white, green and blue LEDs. Also, the performances of the radio seemed not really knowed at these levels. So I want for simplicity : one 3.3V rail, with a regulator that the MCU can bypass during sleep periods if the batteries are > 1.8V.
The RFM chip offers AES Security, in this case, is the authentication chip still usefull ?
Thanks ! I'm checking your work, very inspiring !