FineOffset rain gauge is now also included in OpenNetHome. The new FineOffsetRainGauge-Item keeps track of rain fallen the last hour, the last 24 hours, the last week, the last month and the total amount of rain. The graph shows the amount of rain fallen between each log point, which is every 15 minutes. The resolution of the sensor is 0,3 mm.
Unfortunately, the Tellstick does not currently support this sensor, so it will only work if you use the audio interface with OpenNetHome.
It is available in the nightly build.