I use StandartFirmata project as is, like a Firmware and it is quite big so I don’t know if RFBee chips have enough memory.
Plus merging the two firmwares into one is a little challenging as I’m an arduino beginner 
Firmata over UART works (on Uno/Leonardo) so I assume it will work on Atmega168…
But I will test it on a RFBee chip via its UART soon 