If you have selected to add an approval button to your media asset, you can keep tabs on who has approved of it in the following ways:
Note: in all these cases the 'thumbs up' icon indicates approval.
1. Just hit the 'Info' button when in the playback screen. Expand it and you'll see all the users listed and their approval statuses and more:
2. Hit the little information icon in the project thumbnails list page as shown here:
3. Click any of the user icons on the right side of your playback screen.
Wipster will also send email notifications and activity feed notifications when videos and images are approved. For more on that see this article.