The Activity feed provides a global newsfeed for all Timesheet activity that occurs within your team. The activity can either by filtered by the current week or any previous weeks. You can reach the Activity feed by selecting the Timesheets tab on the main Buildingblok menu, then selecting the Activity tab at the top.
Once there, You'll get an overview of all activity taken within the week in Timesheets. This counts for both the mobile app as well as the web activity. Here's an example of what it looks like:
By Clicking the date range on the top left corner, you'll be able to select any previous week to view.