Searching for weather stations I ran into the wireless sensors on ISM frequencies again. Somehow manufacturers of these sensors seem to want to limit the customer to receiving the data on their equipment. For the well-known wireless sensors on 433 MHz this is 'fixed', nicely described in Sniffing Oregon Scientific Weather Sensor Data. RFXCOM sells receivers which decode a lot of the telemetry and home automation signals. The receiving of oregon scientific sensors is thanks to reverse engineering. The protocol is not properly documented, but I guess it was simple enough to decode.
I asked RFXCOM about the weather sensors on 868 MHz but the lack of documentation on the exact frequency, encoding, protocol I found matches their experience, so they don't offer hardware / software for receiving it. Too bad the makers of the weather stations do not open up their protocols so you can receive your weather station on something besides the display.Anyway, time to fire up the scanner and see whether specific frequencies carry anything which sounds like data transmissions. Maybe some of our neighbours are sharing temperature and other sensors.
Update : Found some time for the scanner and listened while keeping an eye on my watch:433.920 listed in some places as 'oregon scientific' frequency, 433.9250 on my scanner: 22:33:13 databurst 22:33:22 databurst 22:33:27 faint databurst 22:33:52 databurst 22:34:01 faint databurst 22:34:16 databurst 22:34:32 databurst 22:35:11 databurst 433.840 listed in some places, 433.8375 on my scanner: 22:36:07 faint databurst 22:36:59 faint databurstNothing (sofar..) on the 868 MHz frequencies. But the description "instant transmission" can also mean the weather station only sends out data when it has something to report such as a change in temperature or other measurement, and not constantly.
Given the around 40 second updates mentioned by Sean Dague I guess there are 2 or 3 'usable' sensors in the neighbourhood. With no warranty of them staying available. That means it is a bit much to invest 115 euros in for an RFXCOM receiver.