I was able to decode NRF24L01+ and Bluetooth Low Energy protocols using RTL-SDR. with some very cheap analog trickery.

This opens a world of possibilities at the ISM 2.4Ghz band.

Detailed walk-through of the journey from idea to a working solution at http://blog.cyberexplorer.me/2014/01/sniffing-and-decoding-nrf24l01-and.html

Code at https://github.com/omriiluz/NRF24-BTLE-Decoder

Thought it would be interesting for the folks here.

Also, I it would be great if you can add me to the list of decoders at http://sdr.osmocom.org/trac/wiki/rtl-sdr