150kg is pretty heavy and +/- 1-2kg seems quite crude, are those figures correct?
I though you would be wanting to watch the honey come in a jar at a time 
Maybe I am going off at tangents. Bees probably don't mind a bit of movement, so perhaps the hive could be suspended from a spring balance and you just send a picture of several hives from time to time. Maybe you could convert weight to pressure, if that is cheaper/easier to measure.
Sorry just thinking out loud.