This looks promising:
D-Link DUB-E100 USB Ethernet Adaptor
http://www.expansys.com/p.aspx?i=105804
Power consumption is 150 mA @ 3.3 VDC
Power requirement is: USB Bus Powered - 2.5 W, 0.5 A @ 3.3 VDC (+ or - .3 VDC )
A simplier solution would be a USB/RJ45 device that uses PoE (Power over Ethernet). Still googling for this one.

For the GPRS/EDGE/GSM connectivity there is this,
Huawei E220 HSDPA USB Modem
http://www.expansys.com/d.aspx?i=141528
Driver and painfull power requirement discussion is here in this thread,
http://www.gossamer-threads.com/list...4462?page=last

or this,
Falcom Samba 75 USB GPRS Modem (uses 5V through the USB port... unlikely the n810 will like this one, but their home page lists Linux drivers available for it.
http://www.falcomusa.com/consumer_so...hp#Mobile_data
http://www.expansys.com/d.aspx?i=136849

For RS232 over Bluetooth,
IOGEAR's Serial Adapter with Bluetooth
http://www.iogear.com/product/GBS301/
Next step is where are the drivers?