If you've tried using the nRF51822 SDK with the BLE Nano (after following the RedBearLab guide) you may have come to a dead end.
Even the simplest examples didn't work for me. I assumed I had a dead Nano (despite the upload process seeming to work fine).
The reason turned out to be that the latest SDK versions assume you have a nRF51822 chip with 32KB of RAM rather than the 16KB that the nRF51822 on the Nano has.
James Willcox explains this in a post to the RedBearLab BLE Nano support forum.