A good Buddy of mine had a BPW85 so I installed this on the A/D input of a wireless RFXSensor (www.rfxcom.com Order code: 60066, others will also do).

I have been testing with this settings for a while now and its working great. It's measuring light from 0 to 5 volts.
Nice thing about it that its only sending a message when the data is changed and even then it takes like max 60 seconds to send. So fluctuations are very minimal. If nothing changes every 45 minutes a heartbeat message is sended.

On 17:46 the weather became very bad (snow storm) and after that the sun came back again. At 18:30 its getting dark.
Pieter Knuvers
www.bwired.nl Online House in the netherlands. Domotica, Home Automation.