Are there any command line options?

Is there a way to add time to a user, i.e., a bonus 10-30 minutes, via command line? Give kids some extra time when I'm not home (I can SSH in), or unlock a locked out user (because they ran out of time)?

I've been using TimeKpr quite reliably on our home PC to limit my kids usage, and it has been great! No more fighting over who gets to use the computer!