Hi Lars, I'm doing a similar project.
I bought a simple bathroom scale.
Removed the 4 sensors en mounted them on a board of wheaterproof pliwood.
On top of that is my beehive.
This 4 sensors to the INA125 and to the Arduino.
Also I installes a humidity and temperature sensor in the beehive.
Future expansion is a counter to measure the activity at the gate of the beehive.
From the arduino a WiFi module to my home network.
http://www.ebay.com/itm/171495443192?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I have to do this 20 times. Me and my friend we have 2 times 10 beehives.
The final goal is to publish the weight results into HTML to be viewed in graphs everywhere I am.
So how far are you in the meantime?
Regards, Wim