wavemon (Wavemon 802.11 monitor)

wavemon is an ncurses-based monitoring application for wireless
network devices. 

It allows you to watch the signal and noise levels, packet statistics,
device configuration, and network parameters of your wireless network
hardware.

It was originally developed by Jan Morgenstern.

If you use a filesystem that supports posix capabilities, an easy way to
start wavemon as a normal user, while still providing it with all of the
access permissions it requires, is by issuing the following command as root:
# setcap cap_net_admin=eip /usr/bin/wavemon