How to find out last activity time of a session

Hello,
I am trying to identify the inactive sessions in one of my database. V$Session (status) is not very helpful as the status of any conenction becomes inactive as soon as results are fetched.
Is there a way to find out when a particular session was last active (time), or for how long the session is in inactive mode.
In OEM, it is possible to click on session and see "Last Activity On", but, i am looking for a command that i can use for group of sessions.

Thanks in advance.

nv mind...i think i got it...
If there is any better way than the following, pls, let me know:

select username, to_char(logon_time,'dd-mon hh24:mi'), status, last_call_et from v$session;

Why do you want to identify inactive sessions?
Is it because you want to kill them off?