Lowest power, short (10s of meters) range, low data rate, wireless technology

I'm looking for the lowest power (think: fewest battery changes)
wireless comms available:
- short range (ten-tens of meters)
- low data rate (KB/s) but the potential for CONTINUOUS data transfer
   (perhaps layering a protocol to ensure *reliable* transmission)
- need not be "standards" compliant (but must be licensed bands)
- tolerant of other "talkers" in their space
Ignore the costs of network establishment/configuration as "one time"
events.
On paper, it appears that BLE would outperform ZigBee and ANT+
but the devil is in the details.
Anyone using any of these in a *battery* powered application
to comment on their actual observations?