Ad. 1: Try tcpdump. In general, yes, you should always be able to see the devices in the network (provided they are actually transmitting anything)

[edit] oh yes, here you need to be in a monitor mode. I don't know if N810 supports this, but I think I've read that not.

Ad.2
http://ubuntuforums.org/showthread.php?t=506102
It may be blackice, it maybe something else, to little info to tell.