802.15.4 (e.g. based on TI 2500 series) would be great.
My dream solution would consist of the following 3 components:
- a very light version (e.g. TI 2530 + power & antenna circuitry) preprogrammed to send out a packet when one of its inputs changed and change an output based on an incoming packet.
This would service very simple sensors and actuators, all intelligence for this node would be handled else in the network. Battery life is key here, preferably a few years or solar powerable. Sort of smartdust
- a smart version (e.g. ATmega328 or up + TI2520) , basically an RFbee on 802.15.4 + power regulator, so one can run directly of a battery pack, LiPo or 5 V power feed.
This node can do local calculations and take local decisions. It can also command & control the light version. The atmega has an arduino bootloader for easy development, programming via FTDI cable or another Arduino. Low power is nice here as well, but not as important as on the light version
- a bridge version ( ethernet + MCU + radio ) to connect the wireless cloud to the internet
The latter could also be achieved by having a radio+USB connected to a laptop or embedded linux board. Low power is not crucial here as its probably fed by the powergrid.
In all cases cost is IMHO a driver on large deployments. E.g. if we can cut costs by half (e.g. by mass production) this could be a revolutionary change in the internet of things
If you need help with the software side of things then I am happy to volunteer