I found two interesting projects/systems, which were presented at Apimell 2017 international fair of beekiping products and equipment:
Apisfero Bee Varroa Scanner - A cam-based system which, according to their presentation video, is able to precisely count the number of fallen varroa mites on the fallen tray installed under each hive. Still according to the video, the systems looks a bit complex and a bit expensive (there is an array of cams) and also, the check needs the user to be in front of the hive.
Melixa System, a hive monitoring system integrating a scale, a patented sensor able to measure the daily bee flights, a rain sensor, a GPS sensor, other than internal and external temperature sensors. Data is stored in the cloud via GSM/GPRS, and it can be fetched/interpreted by means of a web platform or app. Finally, the system is defined as autonomous in terms of power supply, as it integrates an energy harvesting system (two solar panels). Again, the system seems to be expensive, as they recommend to install the system in only one family.