Okay, after chasing this down for a while, I've come up with the privileges necessary for each of the tabs in the session tool (10g R2):
Main window: v_$session
Cursors tab: v_$open_cursor
SQL Text tab: v_$sqltext_with_newlines
Statistics tab: v_$sesstat and v_$statname
Locks tab: v_$lock
It would be nice if the documentation contained info like this for anyplace where out-of-the-box Oracle permissions are inadequate, rather than assuming everyone who runs the program has the DBA role. Hopefully this will save someone else an hour or two of sifting thru the dynamic tables in oracle...
---dale