after a few "years" of break I'm in love /w Arduino, again. At the same time I'm in love with TP-Link TL-WR703N router, too. Altogether this is the result:
TP-Link TL-WR703N with OPenWRT
Arduino with DS18S20
Every five minuets the Arduino sends temperature data via serial/USB to router. It gets the data and posts it to cosm (ex Pachube https://stats.pachube.com/). Furthermore it writes data to text file that a script reads out. Google Charts showes it then.
Simple as is.