I want to suggest an important improvement that could help a lot to have a more realistic users online list.
As you know, into Settings»System settings»Security»General admin can set the "Inactivity timeout" (number of minutes member has to be inactive for in order to change his/her status to offline).
This is an important feature, but it's not good it is related also with members online list.

I mean that actually:
1) setting a long time (e.g. 15 minutes) it's good to avoid members to not lose their message/comment they are writing if they take long time to write it. Anyway, this affects the accuracy of members online list, because the list shows also members that were online during last 15 minutes, but are not online anymore...
2) setting a short time (e.g. 1 minute) gives a more realistic members online list, but members that take more than 1 minute to write a message/comment are turned offline and when they click to send the message/comment system asks them to login again anche the message/comment get lost.

Well, is it possible to have two different settings to check inactivity time (e.g. 15 minutes) and to update members online list (e.g. 1 minute)?

Maybe it's not a good idea. Anyway I ask to you to make members online list more realistic, avoiding to turn members in offline status if they are still online.

It's very important to do this. Members continually claim that lot of times they try to contact other members which seem online, but they are not anymore...
Sorry to say osDate had a better way to manage offline/online status and give a more accurated members online list. You can do it better.