Hi Beda,
I have started work on a ZDO layer, but it is not yet released.
You can easily get access to the ZigBee Smart Energy standard using the link below:
I have tried to leave libxbee as flexible as possible so that things like this can be implemented on top.
You should configure your XBee to use the explicit frames - set AO = 1.
If you are using xbeeZB modules/firmware, you may need to set it to 3, have a go and consult the XBee manual.
You should use the "Data (explicit)" connection type.
I would have thought that getting something up and running wouldn't be too tricky.
I'd be interested to hear how you get along.
Attie