@slha89: I don't know exactly what your USB network module does.. is it a USB/Ethernet interface? If so, then the N810 would need to be able to support a USB network adapter in its micro-USB slot. It would presumably have to be not just in OTG mode, but in powered host mode too. And you would need a converter cable for USB to micro-USB, if that was combined with power injection then maybe.. of course you would need the USB driver module for the kernel too.

If the use case described above is what you meant to do (checking networks by connecting to Ethernet via RJ45), then I would instead simply bring along my pocket wi-fi adapter.. I plug it into any RJ45 Ethernet, and it's set up to give me a wi-fi AP which my N800 can connect to. Then I'm on the network. The only configuration I would have to worry about would be if the tested network provides DHCP or not, because I would have to manually configure the pocket adapter if it needs a static IP.