taskschd.msc is available in Windows Vista and later.
http://technet.microsoft.com/en-us/library/cc721871.aspx
I could have sworn I’d seen a little task scheduler GUI like you’re talking about prior to Vista, but maybe I was thinking of the “Add Scheduled Task” wizard.
You might have to settle for opening the scheduled tasks explorer with this command:
control schedtasks
I couldn’t find any way to launch the “Add Scheduled Task” wizard from the command line, unfortunately (there has to be a way!)