Using Fivestar to list items that are 'trending' (highly rated in the last week)
Fivestar uses voting API. Voting API stores the individual votes and the total aggregates. You'll either have to create your own aggregates or calculate it "on the fly".

If you have lots of ratings in a week you'll be better off calculating your own aggregates. I would take a look how voting API does the calculation and copy that to your own module. Then modify it to only aggregate votes in the last week.

If you don't have a lot of ratings you can do it in views. Create a view of your type "watch detail". Add relationship "content: votes", require relationship, value type "percent", vote tag (whatever vote tag you are using for those fivestar ratings).
Then add filter "votes: value" >= 80 (gives you all 4 + 5 star ratings), "votes: timestamp" > "-1 week". Check to make sure you'll see the correct ratings show up.

Now turn on aggregation, add "nid" and use "count distinct" to show the number of ratings for each node. Then sort by that value.

Turn on query caching to make sure the view renders quickly for future requests.