Couple of options: 1) Report within your app:
are your employees entering their time through your App?
If so, you can create a table view of for each employee that is based on a slice and date range that they can view it in your app.
It will require user sign on.
This functionality would likely be best as a separate app that uses the same tables. 2) Emails to all users with monthly timesheet results:
You can create a workflow that outputs timesheet totals or timesheet details to each employee. Hope this helps.