I just learned that the new macbook airs and macminis have bluetooth 4. (21-july-2011) with the iPhone 5 rumored to contain it. Assuming that includes the low-power mode, the sensor network is finally here. Oh wait this is Apple - they'll neuter it before shipping.
lowpower bluetooth4 is our best hope for spontaneous phone to phone discovery and messaging. (re: dating site)
— Dec 2012
Bluetooth 4le breakout boards
Client only Chip: NRF8001 https://github.com/nabilt/nRF8001-Breakout-Board Part: $2.50 http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=46669
Master/client Chip: BLE112 http://www.inmojo.com/store/jeff-rowberg/item/ble112-bluetooth-low-energy-breakout/ Part: $18 https://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=46652 TI CC2540 http://www.mouser.com/ProductDetail/Texas-Instruments/CC2540F256RHAT/?qs=sGAEpiMZZMsyM1rGGtQxrPlhStm%2fMGm9
TurnKey $50 out of stock, new version arrives Jan 2013 http://www.inmojo.com/store/jeff-rowberg/item/ble112-bluetooth-low-energy-breakout/
— March 2013
With extra stuff? $13 http://www.rfdigital.com/?targetpage=item&filterpn=51822
breakout board ?
— April 2016
smart bluetooth / BLE TI CC2640
ATMEL ATBTLC1000 http://www.atmel.com/devices/ATBTLC1000.aspx