Last year and the year before the news was all about the Flow Hive. Now from Germany comes a hive that kills varroa... the hive itself kills the mites. It's called the Thermosolar Hive and there's a video online by Hashem Al-Ghaili at: https://www.indiegogo.com/projects/thermosolar-hive-healthy-bees-healthy-honey--5#/ The theory is that a sustained heat in the low 104-116 degrees F for about an hour and a half will kill 95% of the mites, even in the brood and not injure the bees or brood. Of course the product is very expensive but the idea is very interesting!
May your days be sweet!