http://www.nordicsemi.com/eng/Products/ANT/nRF24AP2-1CH
:o Also available in 8 channel and USB version (single chip usb ANT interface). Seems pretty awesome.The nRF24AP2-1CH is a highly integrated single-chip single-channel ANT™ Connectivity IC. It includes an ultra low power 2.4GHz RF transceiver and a fully embedded enhanced ANT protocol stack, plus a flexible serial interface supporting a wide range of external application microcontrollers. Offering sub-17mA peak currents, average currents as low as 11μA. and a 1.9 to 3.6V supply range, the nRF24AP2-1CH supports extended battery lifetimes of months to years from a single coin cell. This ultra low power operation also makes the nRF24AP2-1CH ideally suited to battery-operated ANT devices such as HRMs (heart rate monitors), speed-distance sensors, and bike speed-cadence sensors.
The integrated 2.4GHz RF transceiver core is based on the nRF24L01+ and provides significant sensitivity and co-existence performance improvements compared to Nordic’s previous generation nRF24AP1 IC. The on-chip ANT protocol stack features full compatibility with all ANT+ profiles and includes advanced features such as: Scanning Channel applications demanding low latency performance, improved Channel Search for less impact on active channels, and a per channel-based TX Output Power Control and Frequency Agility mode for improved co-existence performance.
Unfortunately the only store I found selling them is http://www.semiconductorstore.com but they charge over 60$ for international shipping.