Our son was two weeks late entering this world, so I spent some time designing a data logger around nRF51422. It will never be put in production. There are now better RF SoCs around, but I might reuse some other parts of the design.
Schematic and video: <a href="http://www.loligo.se/Logger/" target="_blank">http://www.loligo.se/Logger/</a>
Components
1×
nRF51422
ANT and ANT/Bluetooth Smart multiprotocol SoC