Is it possible to get the QNH value in Austria using a web service? I got a altimeter sensor which can be connected to a computer and can be adjusted by the QNH!

I need the QNH for Austria, I figured out that the current QNH of the airports are streamed via radio.

Are QNH provided as text format or even better web service, so I can fetch mine automatically for transparent altimeter setting?
The current QNH at an airport is included in METARs so you can grab it form there. There are a few online services to retrieve the METAR automatically, such as this one (using Vienna airport as an example).

The latest METAR when I wrote this answer was:

LOWW 281050Z 14010KT 9999 FEW040 SCT065 BKN300 04/M03 Q1012 NOSIG


which shows a QNH of 1012.

Note that depending on the country the format may vary slightly, but in Austria (and European countries) you should always find a Qxxx value in the report.