Very simple parental control. Users have limited time on the computer.
Possibilities:
- per-user control
- start and and time, outside of which a user may not log in
- maximum time per day
- grace time (displays a popup warning the user that the max time or end time is almost reached)
- screensaver aware
- global, per-day and override controls + profiles
- Gnome-shell extension to track the remaining time