Arduino already has an Ethernet shield and WiFi Shield that enables it to send data to the net. But these options aren’t the only way of doing this. Martin have managed to use TP-Link TL-WR703N router to do this task. As you may know TP-Link is a little nice router that can run OpenWRT which his actually a Linux.
Martin hooked up an Arduino to PCB points where serial interface is. This way he was able to send serial commands from Arduino serial port to Linux console. He found out that console is sensitive to high serial speeds and can corrupt receiving data. He had to slow down serial data stream by writing a helper function where each character is sent with some delay. Anyway by overcoming several roadblocks, he was able to talk Arduino to router interface and send sensor values using this router as a shield.