Recently I noticed the ESP8266 WLAN dongle which is remarkably inexpensive and sells at a local retailer for less than 10 Euros and much less on the net. The dongle talks WLAN on one side via a built-in patch antenna and TTL-serial on the other side. I bought a dongle and hooked it up to an Arduino on a breadboard. Following the documentation and tutorials available online I quickly had it connected to the WLAN at home and received an IP number via DHCP. Standard WLAN security with WPA2 is available, but the Arduinos are not really powerful enough to handle any serious authentication. I therefore decided to use a Raspberry Pi as a router to span a private WLAN and use port-forwarding to make a single port on the Arduinos visible to the outside world. Thus we have path from the individual sensor to any computer on the weird-wild-web for a few Euros. I sketch this infrastructure at my WLAN Sensor Net project web site and will use it both at home for all sorts of sensing and automation applications and at work to connect sensors in the lab to monitor all sorts of signals and provide a standard interface to our EPICS control system. Since bare ATmega chips can be flashed with the Arduino boot-loader at minimal expense, installing many sensor nodes is feasible, even on a limited budget. Maybe there are other elektor-labs readers who find this interesting and can use this approach in their projects and also contribute with code for other micro-controllers and many, many sensors and things to control. One thing that bugged me is the high power consumption of the WIFI dongle. I will recycle old phone chargers that provide 3.7 V or so to power the circuits, but maybe someone has better solutions. Advanced sleep mode and wake up once in a while? Recharging a supercap with a solar panel?