It is meant to be used in conjunction with these apps. The idea behind Reminder is that although the NewtonOS has many ways of gathering Personal and Contact information, there isn't a good overall way of being reminded of it. Or that you have an incomplete call to an important client. Put simply Reminder is a nag. But a helpful nag.
Reminder is fully configurable to allow the user to choose which reminders are neccessary.
There are even three personas to choose from. Get your reminders in a fawning, neutral, or attitude laced tone. You will be reminded of any meetings for the day. Other wise Reminder will prompt you during the reminder interval. Any calls that are not marked 'Call Completed' will be shown.