i got a beer-view-mirror. some dude assembles them at his kitchen table. they are $12. it works very well. you have the choice of your favorite brew (if it isn't too exotic).
the beerviewmirror store is here:
http://www.beerviewmirrors.com/
you can make one yourself following the instructions here:
http://www.instructables.com/id/Beer-view-mirror