Using the most recent VSIDO build and have discovered that, with Sid, update-notifier has a whole bunch of gnome dependencies now - like pulseaudio - that weren't included before (not that I recall anyway). So to check for updates, I am using the:
aptitude search "~U" | wc -l
method in conky that many are familiar with. Found a variation a while back that I like though - these are not my scripts:
This script checks for updates:
chkupdates.sh
#!/bin/bash
sudo apt-get -qy update > /dev/null
NUMOFUPDATES=$(aptitude search "~U" | wc -l)
echo $NUMOFUPDATES System Updates Available
if [ "$NUMOFUPDATES" -ge "1" ]
then uxterm -e ~/bin/ask-aptitude-updates.sh
fi
exit
and for the purpose of this example, will launch uxterm if there is more than 1 update available - change the "1" to "20" for 20 updates and so on ...
ask-aptitude-updates.sh
#!/bin/bash
echo "Aptitude Update System? y or n"
read -t 12 userconfirm
if [ "$userconfirm" != "y" ]; then
echo "Aptitude Update Cancelled"
exit 1
else
echo "aptitude updating system..."
sudo aptitude update
# sudo aptitude -y safe-upgrade
sudo aptitude safe-upgrade
echo ""
killall -SIGUSR1 conky
echo "aptitude update complete. Will now exit..."
sleep 3s
fi
exit
will launch uxterm (any terminal will work) and has a 12 second usercomfirm to update the system or it terminates. So the whole process is interactive and will not update your system unless prompted to do so.
If you just want to check for updates:
apt-update.sh
#!/bin/bash
sudo apt-get -qy update > /dev/null
NUMOFUPDATES=$(aptitude search "~U" | wc -l)
echo $NUMOFUPDATES
exit
Since the output is an integer only, it can be used with if_match, else, endif to give it some colour.
The result:

I suspect an interactive conky could be made out of these so that clicking on the updates would launch the update terminal.
Edit - changed " sudo aptitude -y safe-upgrade" to "sudo aptitude safe-upgrade"
Normally use this script with stable/testing; the -y flag probably not wise with sid.