You can now easily check which PEPERONITY user is now online. Just visit his/her site. and scroll the page to the end. You can see his status(weather the user is online or not) in the side of his profile. Similarly, you also see status while reading someone's mail.
Similarly, Other user can also check you weather you are online or not.
If you want to hide your status from other user then you can make this option inactive. To disable this option first you have to come to your 'my area' . Click 'my profile', then click 'Privacy'. Click there and scroll to 'DISABLED' to inactive this option.