I'd like to avoid frequently replacing batteries or running power wires to the boxes if at all possible, as such, I'm either wanting to have ultra-low power components and 'smarter' operational times (eg only show LED's when someones in the room) or using solar power to provide the juice.
Another option would be to use 'wireless power' like that which is used to power some recent mobile phones; but this requires running wires on whatever surface you'd like to put the boxies on - which sort of breaks my 'no wires' rule.
So Solar power seems to most logical step to take, and based on no strong evidence, I think I'll be needing a 0.5w solar panel per device.
The components most likely to be in the boxies are;
* 1x MSP430 ( MSP430G2232IN20 )
* 1x Nordic RF24L01+
* 1x RGB LED - Unsure which one specifically yet - maybe a programmable one from an LED strip
With those components, the peak current draw is likely to be around;
* MSP430 - 220 µA ( datasheet )
* RF24L01+ - 13.3mA ( datasheet )
That gives a total of 75mA at 3.3v which is around 0.25w of always on power.
So then i think - why not buy 10 of the garden LED lights I keep seeing around the place, and butcher their internals for solar power, charging circuits and batteries...