I've seen a contraption for treating mites in a newsletter.  It is a box that
sits on top of a hive body amd has a hose that leads to the entrance. It
supposedly works by heating the whole hive contents to 120 degrees F,
and this allegedly kills all Tracheal mites and all Varroa not in the
cells.  Supposedly this doesn't harm the bees.  Think it needs electricity
available.
 
-Mike