I was just trying to find something similar, but I'm more interested in the step-up part, to use with one or two AA/AAA to power my circuits. That was the closest thing I found from "reality": https://www.kickstarter.com/projects/340271897/whisper-node
I tried to build a step-up circuit myself but wasn't that easy... looks like those switching regulators don't work very well in breadboard, they're all SMTs with very fine pitch and they need other components like the inductor that can add some cost. Also found those ones ready to use: https://www.pololu.com/product/2561, it's not the most expensive but I'm not sure if they will keep the power consumption low at stand-by.
You mentioned 100mA and one year... are you planning to sleep those power-hungry components most of the time correct?