You can basically tell the Lookit to capture the entire screen or define an areas specifically. The uploading URL + few other options can also be set using the preference window. If you want to automatically shorten the URL of the uploaded images then it can even do that as well.
So if you use Ubuntu 11.04 or 10.10 (should work on 10.04, I think) then you can easily install Lookit using its official PPA channel. To do that, simply open your Terminal and issue the below command.
sudo add-apt-repository ppa:lookit/ppa
sudo apt-get update
sudo apt-get install lookit