Hi Evan - AFAIK the only way is to hit refresh since tableau does not auto refresh once a view/workbook in opened for viewing. You need to reopen it again or refresh it.
If you embed the visualisation on a page which refreshes itself every 15 minutes (<meta http-equiv="refresh" content="900"> in the head of the page), and refer to your visualisation with '&:refresh in the URL like this:
Let me know if this is a possible solution for you!
Johan de Groot