I think it would be great if there could be a time tracking reminder that would go off once a day if a person was logged in and had tracked less than an hour of time in the last 24 hours. It should have a "Don't show this again for x days" option. I think it would be a good way to nudge people who mean to track time, but get into what they are doing.
It would be cool if they opened a task assigned to their user and due today or past due for it to trigger.
It could even be as small as the time tracking icon scaling up 200% with a CSS animation or something like that, to attract attention to it.