How secure is a bluetooth keyboard against password sniffing?

In a situation where an admin will enter sensitive information into a keyboard (the root password), what is the risk that a bluetooth keyboard (ship by default with Mac systems these days) would put those passwords at risk?

Another way of asking would be: what security and encryption protocols are used, if any, to establish a bluetooth connection between a keyboard and host system?

Edit: Final Summary

All answers are excellent. I accepted that which links to the most directly applicable information however I also encourage you to read Nathan Adams's response and discussion about security trade-offs.

Solution 1:

http://en.wikipedia.org/wiki/Bluetooth#Security

While Bluetooth has its benefits, it is susceptible to denial of service attacks, eavesdropping, man-in-the-middle attacks, message modification, and resource misappropriation.

Solution 2:

I'd suggest looking at this publication by the NIST. It provides some pretty useful information on Bluetooth security. The encryption protocol of bluetooth is E0 which is 128 bit.

http://csrc.nist.gov/publications/nistpubs/800-121-rev1/sp800-121_rev1.pdf

Solution 3:

Although bluetooth may not be the most secure protocol, you have to put things in perspective: Bluetooth has a relativity short transmit range. This means that if you were to use bluetooth keyboards in a building, a person would have to be in the same room or close to the room to actually do anything malicious.

Just because a certain technology is insecure, doesn't mean that it is useless.