I'm very interested by your setup. It has been a shame to have some low voltage power in order to measure power consumption
I hope you can display something soon.
Regards,
Qq.
This is a WORK IN PROGRESS !
This has not been yet tested, but the power supply part is based on a schematic found somewhere on the net.
It should be possible to power the atmega + RFM module and allow sending frame once a second.
I still have to test the power stage to see if it can power an atmega + some mA for a RFM.