Can a external wireless lan be a substitute for ethernet?

[efflandt]

What you are looking for is a "wireless bridge". I have used what I think was an older version of this one that was wireless G (this one also does N):
http://www.netgear.com/home/products/con...E2001.aspx

Note that it needs to be powered, but besides a power brick it comes with a cable to power it from a USB port.

You probably initially need to connect a computer to it to configure wireless security. But after that your BluRay player should be able to automatically connect. Although, some players can be more automatic about connecting than others. I have a Samsung player that automatically connects and checks for updates, but my LG player seems to wait until I check network settings (don't actually need to set anything) then it automatically connects.