Parental Control application for Linux is bit hard to find, if you encounter any then it may be outdated or just don't work as per your wish, they just restrict internet access or sort of stuff. If someone uses your computer or you let your kids use your computer. You can restrict access for them as you want, from now you don't have to say your kids to leave computer, Timekpr will do it better. You can call Timekpr restriction application or parental control application, whatever you like to call it.