Similar to the Sibme web version you also have the option of adding time-stamp comments while using the iOS app. On the Sibme iOS app you have the option to add both text and/or audio notes or comments. While watching the video you can add a comment or note by either tapping the video player or that "add comment/note" area below the video player.
A tooltip will appear on the video timeline, which will allow you to post your comment. You can do this prior to upload on videos that are saved on your device within Sibme in Offline "Videos" or you can do it after the video has been uploaded to your Sibme cloud Workspace or to a Huddle you are participating in. You also have the option to reply to Huddle participant comments within Huddles.