Additionaly to what's being said already, the bing utility will give a rough estimate of the available bandwidth even without a client-server setup.
I would agree that even ping can give some interesting data - especially packet loss, round-trip-times and mean deviation for RTTs are directly streaming-relevant data. Of course, you would need to run ping with appropriate packet sizes (i.e. the sizes your streaming protocol is going to use) and the necessary frequency (i.e. as often as your streaming protocol is going to send). For a quick glance at a customer's site we are using this kind of script run every minute and evaluate the results:
# Time ping is run (in seconds)
# size of the ping data (in bytes, without header data)
# destination IP
I=`ping -q -s $PSIZE -i 0.09 -w $TIME $DEST | egrep '(packet loss|rtt)'`
echo `date` $I >>/var/log/latency_voip.log