I was actually just coming here to post about the airports/snow leopard. Apple calls it “wake on demand”. It is one of the big advantages to control both pieces of hardware (router and server). It is a pretty awesome behavior. I want to see if dd-wrt or tomato supports a similar functionality.
Conceptually, it isn’t that hard. In my head, you register certain services with the router for a given host. The router obviously has to do a few more intelligent things (remember the hosts mac/ip, keep track of the servers state). I feel like conceptually it isn’t the hardest task to make happen.
Obviously, apples behavior is ideal. I have never configured an apple server, but I can imagine it’s as simple as…”Yes, I want an ftp site. Yes, I want WOL. Yes, I want my router to manage this for me”. I would think the server communicates this stuff to the router and it is all instantly configured for you. Seems very Apple-y.